At long last, here is my review! I hope no one minds, for this review I'm only going to discuss the scenes with Wendla in them, because I know those are the ones people care about in this case.

If I try to include everything I will never ever finish this! I do have lots of thoughts about Taylor and Jake in particular, who I hadn't seen before they rolled into town, but I'm going to try to do that in a separate review or I will never get this thing done.
Pre-show - Breaking my own rule already, as this has nothing to do with Krystina, but there was some stage seat drama before the show. Someone messed up because all the audience seats except BB8 were full when two more men were led onstage, so the usher plopped them in AA16 and BB10 and left them there. They were still sitting there when the ensemble came onstage. It was Krista and Justin on stage left. They didn't say anything for a long time but then as the usher was about to walk away I saw Justin pull him aside and whisper something in his ear. STILL the two guys weren't asked to move. The initial pre-show announcement had been made and the band members had taken their places and were ready to go. Another minute ticked by, and then FINALLY a woman with short blonde hair (who I'm guessing is with the SA company) came out and asked one of the guys to move to BB8 and escorted the other guy offstage. The show finally began about 5 minutes late because of that.
There was no understudy slip in the program and I was disappointed when Krystina wasn't announced in the pre-show announcement either. I guess they put it up on the understudy board in the lobby and that was enough, but I thought it was too bad that it wasn't mentioned separately.
MWBM - This was really really beautiful. Krystina's voice is gorgeous and pure. It was interesting to get to see her the day after seeing Christy. To compare them directly, Christy's voice has that bit of...roughness?...around the edges, kind of that folky/mixy quality that is really beautiful. Krystina's voice is completely different. Her tone is more pure and she has this crystal clear belt and a beautiful vibrato.
In general I found Krystina a little less facially expressive than Christy, but that didn't keep me from really enjoying her. MWBM was beautifully done. She struggled a tiny bit on the highest notes toward the end of the song; it sounded like they were right on her break and she was trying to figure out whether to belt them or mix them.
Really the only negative thing I have to say about her is that she has a bad habit of pursing her lips together quickly between phrases when she sings, as if trying to wet her lips or prepare for the next thing she's going to sing. I noticed her doing it in this first song and found it distracting from that point on whenever she would do it. I'm sure it's just a nervous tick that she'll be able to ditch in the future.
The Stork - Very cute. Krystina didn't play it for quite as many laughs as Christy does. For example, Christy got laughs when she gestured her mother to the chair, and Krystina didn't cheese it up as much. Very good rapport between Krystina and Angela.
MWBMR - So fierce. Krystina really belted it out, especially the last chord. Her movements were really powerful too, and she and Steffi D sounded great together in the first part. The five of them with Krystina at the helm was really something. It was nice to hear it belted, as compared with Christy's mix.
Taylor ROCKS out during this song, and at this show he had an enormous grin on his face the whole time watching Krystina as he danced and bobbed in his chair. It was adorable and fun to watch.
Such a radical - Krystina played this a little snottier than Christy does. When talking about the wedding she was really defending her mother and agreeing with her, and didn't seem to express as much regret that she couldn't attend the wedding (as opposed to Christy who plays it like she's sad and kind of embarrassed about her mother's stance on the issue).
My Junk - Very very cute! I could tell Krystina was loving it and relishing her chance to jump around and have fun.
What Serves Each of us Best - I thought Krystina's Wendla seemed a little less sure of herself, less sure of her convictions, and more nervous about speaking with Melchior than Christy's, whereas I always get the sense from Christy that her Wendla has given some thought to their acts of charity and the effect they have.
Krystina is a little taller and bigger than Christy, so she and Jake make a different picture together as a couple. Melchior runs up to Wendla excitedly and gets right in her face on, "Wouldn't that be remarkable?" and when it's Jake and Christy, he really towers over her and she looks so small. That effect was lost just a little bit with Krystina, but other than that, they actually seemed like a better match physically than he and Christy.
The Word of Your Body - This was really beautiful on Krystina's part. As I said above, her voice is so clear and pure, and it was perfect for this song. Again, some of the higher stuff she struggled with a little bit and it affected her pitch a little bit in a couple of places, but overall this was beautiful.
Martha's Secret - Krystina was fun with the "Tomorrow I'm bringing scissors" line; she said it in a sing-song way like kids do when they tease each other.
Beating Scene - There was NO laughter during the beating scene. None. Krystina and Jake did a great job and the progression through the scene seemed really natural. She didn't get as worked up as Christy on the "I've never felt...anything!" part, but it worked. In my opinion Krystina's Wendla seemed a little less manipulative in this scene than Christy's. Christy makes it clear that Wendla is making up the story about dreaming about her father whipping her in order to bait Melchior. I didn't get that sense as much with Krystina.
I know I said I was going to focus on Wendla, but I simply have to gush about Jake Epstein in this scene. I am pretty new to Spring Awakening so I only ever saw Kyle as Melchior, and I just didn't really "get" this scene with him in it. DIdn't get why he seemed so cold to Wendla at the beginning; totally didn't buy his "I'll teach you to say please," etc. I still think the scene is written awkwardly, but Jake Epstein sold the beating scene for me. I get it now. Perhaps this is due to different direction as well (the SA veterans will have to let me know), but whatever it is, I am impressed. More in my next review!
The Hayloft - Again, I have to take a moment to praise Jake Epstein in this scene. His acting was incredible and was a whole different Melchior than Kyle's. I always thought Kyle seemed like kind of an a-hole here, like a frat guy trying to say anything to get into Wendla's pants. This was especially true for me as things escalate and Wendla objects, Kyle's "WHAT?"s always seemed annoyed, like, 'WHAT??? Why won't you just let me into your pants?' But Jake plays it as if Melchior is just as freaked out and unsure as Wendla. When she is lying down and she objects and he asks "What??" it's like he's really scared, like she startled him and he wonders what he did wrong.
Krystina and Jake were great together in this scene. One small detail is that Krystina actually braced herself and you could see that it hurts Wendla when Melchior finally, um, enters her. I've never noticed that with Christy. Anyway, this was well played by both of them and all of the desperation and uncertainty came across well.
The Guilty Ones - Both of them did a great job transitioning from the intensity of the sex to the awkwardness afterwards. Krystina sounded great again.
Anemia - It was cute to see Krystina in the nightgown! That was not meant to sound creepy; it's just fun to see a diferent actress in the iconic Wendla constumes. The "But I am not married" line got a lot of laughs, and Krystina did a good job playing the big emotions in the scene. I thought she and Angela played well together.
Whispering - You could really hear the tears in Krystina's voice at the beginning of the song. It was the first time her tone was anything but completely smooth and clear, so the effect was dramatic. Again, her face was not quite as expressive as Christy's, but still I thought she did a good job going from scared and ashamed to hopeful.
Those You've Known - I wanted Krystina to belt out the "I Believe" but she sang it in mix. I was a teensy bit disappointed, but it was still powerful and she sounded great.
Song of Purple Summer - Krystina was glowing and soaking up her last few moments of her day as Wendla. The cast is sounding so good on this song. The chords ring out so beautifully, especially during the a cappella section.
Overall I really enjoyed Krystina's Wendla and the new things and different sound she brought to the role. I hope she gets another shot at Wendla before the tour is over.