I had just watched the episode on Hulu a couple of hours before I read this review, so this kind of helped put my thoughts on it into words...by which I mean my thoughts were basically the same as what Bob described, but now I understand them: the episode didn't quite have the sense of closure I was expecting from a season finale - although granted, part of that might be because I watched it online on a relatively small-screened laptop, so I didn't immerse quite as much as I might while watching something on a TV - but I also wasn't particularly disappointed by the episode itself in spite of that. Garrett was dealt with in a satisfying manner, May got her throw-down with Ward (surprisingly, the show's stepped up the comedy in the last couple of weeks: "prepare for a large file transfer" last week, and "you were never on top" in the finale both got me to genuinely laugh out loud, which doesn't happen much), the crew officially got the season 2 mission everyone pretty much assumed they would get (though 'Director Coulson' was a nice touch I didn't expect), the cast seems to have mostly sorted itself going into that mission (Ward has been replaced by the less-generic Triplett, and Fitz is still alive but out of commission, shedding the somewhat-extraneous extra 'sciencey' member of the crew), the most intriguing villain by far (Raina) escaped and continued doing intriguing things, and the main mysteries going into next season have been set up (the effects of GH-325 on Coulson, the identity of and inevitable encounter with Skye's parent(s)) and look like things that will actually have relevance to the plot of the show/episode beyond "okay, well, now we know that," which is good.
On the Inhuman angle: the big thing for me that pointed in favor of that particular theory popped up during the conversation between Raina and the possibly-actually-clairvoyant-now Garrett. First Garrett, in talking about how humans are unevolved describes the process of further evolution as "crawling through the mist" onto land - specifically mist, rather than more common terms like mud or earth or whatnot, to the point that it felt more like a specific nod at the Terrigen Mists, which are what trigger the onset of abilities and mutations in Inhumans, than just a figure of speech. Then, right after that, Raina asks "what will [she] become," which...would definitely fit in with that whole angle. Raina is definitely something relevant, probably a similar something to Skye, but finding out just what that something is should be fun. Me, my bet is still on both of them being Inhumans - and since the Inhumans were Kree-created (Kree-ated?), that also makes sense with the connection to the GH-325 and its likely/possible reference to Guardians of the Galaxy. It's not a certainty, but it makes a whole lot of sense.
(...crap, now I'm going to have to wait until when Guardians comes out in August to get my next MCU fix. Damn it all.)
(Also: it wasn't something that was noticeably lacking in the first season, but hopefully the fact that the show is doing well means they'll get an improved special effects budget for next season, right? I feel like they did pretty well with what they had, but the idea of this show getting more special FX stuff to work with is an appealing one, since it means more creative freedom, and generally more possibilities for including stuff.)