Just finished the game. Took about 3 hours and I spent loads of time looking around.
Yes, took me roughly 3 hours, maybe a little more, to finish it. Did everything according to the credits and I also _feel_ like I've done everything. Talked to everyone, listened to all the voice acting, explored and clicked on everything. I'm sure there's plenty of details to be missed in one playthrough, but probably nothing major (unless it requires specific actions).
My verdict for now: I think this game is pretty great. The humour is hit-or-miss which is, of course, to be expected. I can easily point out the parts I didn't like - chapter 2 wasn't that funny aside from one character that's in it, and the final stretch felt a bit contrived (still had some amusing elements, though) - everything else ranged from dumb/witty to hilarious. Not often do I laugh at a video game, so I try to give due credit when it happens.
As far as voice acting is concerned, I didn't like all the robotic voices and robot characters (except the lady robot from the first level). The rest of the cast is pretty much fantastic in an over-the-top satire sort of way. Love how the VA plays off of the subtitles and vice-versa.
There's also a lot of little bonus games hidden in Jazzpunk, all of them parodies. Again, as you'd expect, some of them work (Quake one is the best), others are a bit grating. In general, I'd say they feel a tad disjointed from the rest of the game - others may end up really liking their inclusion, though.
Overall, I think this game is definitely worth experiencing for the many highlights, not exclusively of the comical variety. Game has a great sense of style and I really enjoyed the set pieces. Surprisingly, the art surrounding this game is rooted in the, admittedly ridiculous, narrative and there's one really cool looking sequence where it becomes apparent. The thematic consistency is something I did not expect.
Last thing I'll say: It would be nothing short of a crime if they didn't release the soundtrack. I dare them to withhold it.
Looking forward to spoiler talk!