This episode was very solid, but PP in the way ruined it for me. It felt like an invasion in some good ongoing storylines. Let's see:
I) Storylines and events I liked.
A) Like a virgin. It was a funny way how everyone revealed how they lost their virginities. But it was unexpected to find out that April hadn't cashed her V-card yet! What an epic moment! And how Cristina reacted and made fun of it was a brilliant move. And now it makes her character more interesting! With who will cash her V-card? Mistery, mistery! She's an appealing character, and the bar scene made me think that she's very smart and maybe she'll get the respect she deserves (watch 7x04, 7x07, 7x20, 7x22)
B) Alex's PTSD. It was an interesting develpoment for Alex's PTSD storyline. And I liked how the Chief tried to solve it, and how helpful he was.
C) Cristina's PTSD and Derek. Clearly, Cristina wasn't ready to get back to the OR. But I liked Derek's support and trust. But it was hard to watch how Amelia joked about it. Cristina's PTSD is more serious than we think, and it is a storyline worth watching.
D) Teddy's frustrated love. It was funny to watch, how she reacted to the ending of the relationship. It was expected, but still was worth watching.
II) Dislikes of the episode.
A) The way that the wart disease was treated. Even the comparisons were a little bit morbid. The case was being treated well. That spider surprise scared the hell outta me! And it was funny because it happened just before Bailey's phrase "you have to deal with everything that comes out of the human body). But the emotional storyline was not enjoyable at all. What's that of "what if love is not enough?". She should have been supportive! It's not fine to leave him alone with no-one to be beside him!
B) Amelia/PP. This intrusion spoiled the entire episode. Even if Derek and Amelia had a chance to talk to each other to put their affairs in order, it ruined the entire episode. I did not enjoy her mocking Cristina and those "shooting" metaphors she kept repeating. If I wanted to watch Amelia I would have tuned in PP! This is GA, not PP, and it feels rare to see another show being taken for granted in another show... not all of us watch PP! Don't treat us as if we do! (hated 03x22,03x23, some parts of 05x15, 8x15) And the worst of all, she spoiled (delayed) Lexie's chance with Mark. What for?! This doesn't add more to the show, and it temporarily destroys this love/no-love storyline between Lexie and Mark! It was unnecesary.
C) Arizona's request. It was cruel that Arizona wanted Cristina to move out so abruptly after all that happened. Callie was right to state that "we're monsters for doing this". It was annoying that this desire was shown the entire episode. And the way to make move her out? I've seen it in 02x22 with that hot Burke-Cristina scene. Not original at all!
To sum up. It was a solid episode... but PP invading GA destroyed the episode (would have rated it with "6" otherwise).