The 3-D worked pretty well for most of the movie, but there were a few cases where it seemed like either it made the motion blur worse, or else I was not sitting in the right part of the theater. The 3-D shots in space worked best; a lot of scenes with humans didn't work as well, and I was reminded of a ViewMaster.
Robin and I discussed which monsters we liked best. He likes Bob, the blob, while I went with Dr. Cockroach, the mad scientist. I particularly liked the various SFnal references, from the "Close Encounters" theme to "Dr. Strangelove" and even (*gag*) Star Wars prequels. The balance of humor in the movie was pretty good, with both jokes aimed both high and low. (I do wonder, however, what sort of wedding dress sustains a 10x change in size with only minimal loss of modesty. This was not the sort of movie willing to make jokes about that--- other than a flying garter.)
One thing I wish had been done better is to really get into the theme of how the "monsters" might re-assimilate. Susan is so focused on getting back to her "old life", but the only valid alternative seems to be super-heroing. Why couldn't Susan work in construction, or Bob in toxic waste disposal?