In my opinion it could've been better. Shifting POV is perfectly fine, but I prefer it remain from a third person perspective when doing it, makes it easier to understand. I wouldn't have minded extra details as well. It seemed to leap into the story a little too quickly with the AiCon stuff, it seemed that we're talking about the antidote and Ai's feelings, and we suddenly discover Shinichi has feelings for Ai...I prefer AiCon stories where Conan gradually realizes that he is in love with Ai, much more realistic.
Now, if Gosho Aoyama had hinted that Conan had obvious feelings for Ai that went beyond friendship, it might make sense, but since this has not been shown to such an extent that can be said that Conan truly likes Ai over Ran, this fanfic seemed a little rushed.
In Chapter 2, Shinichi felt extremely OOC over Shiho's clothing. Ok, so she looks beautiful. That doesn't mean Shinichi goes and says, "You're going to wear that from now on." Way too commanding, making me feel extremely disappointed in him and dislike him for that.
I haven't gotten much farther, and since I'm not supposed to be critiquing the fic here, I shall leave it at that. Though I really wish that the author would choose whether or not to use honorifics...the switching back and forth does irk me a little...
Either way, it isn't the best work I've read. Perhaps when I'm through I'll review the story and say a little about it.