Finally saw this last night, at a movie night hosted by an old colleague of mine. There were almost a dozen of us there, and it seemed like the majority of us didn't care for the movie, which surprised our host (he and his wife were the only ones who had seen it before, and he hates most "Christian movies" but had said good things about this one).
The most vocal in their dislike were a couple who are big fans of the book, and who felt that the movie missed what made the book work; the word they kept using was "contrived" to describe all the various plot mechanisms that the movie introduced.
As for me, if I had to sum up my reaction in one sentence, I think I would say that this felt like a Steve Taylor album and I want to see him make Chagall Guevara albums again. In other words, this is very much a Christian subcultural product, made by and for the Christian subculture (or at least the segment of it which uses four-letter words, drinks beer and dislikes Republicans), and it follows many of the narrative beats that I would expect of a "Christian movie" (there are a couple of "reveals" at the end that were absolutely unsurprising). And some of the straw-men set-ups, like the debate at the bookstore, brought to mind some of the weaker moments in Taylor's songwriting (where it's always the unbelievers who are cowards or cynics and the believers who are brave and sincere). And it didn't help that the blonde love interest, i.e. the character who is supposed to draw our protagonist back to faith of some sort, was probably the weakest link in the entire film, acting-wise; I honestly couldn't help but think of the acting in movies like
Fireproof whenever she was onscreen. But what I'd really like to see Taylor do at some point is just Make A Movie without worrying about what sort of audience his film will have, or whether it will fit into some corner of the Christian subculture.
Two other words I ended up using in our post-screening discussion were "self-conscious" and "deliberate", in reference to not just the writing but also the cinematography, e.g. the way that, even fairly late in the film, a shot of the laundry room has a bra rather prominently placed in the frame so that we are reminded, yet again, that this is a Mixed Gender Facility and that our protagonist is Seeing Things He Never Saw In His Good-Church-Boy Days. I would have preferred that stuff like that just be part of a naturalistically detailed background.
One of my colleagues (not the host) also quibbled with the fact that the film seemed to paint Southern Baptists in a consistently negative light, while giving more credit to Episcopalians (or whatever that one church was). I also wondered why the resolutely Protestant protagonist felt he had to "apologize" for things that had basically been done by Catholics (the Crusades, etc.). (The film does refer to Catholics doing good things, too -- in Canada, at least.

By the way, do Catholics really get their communion wine from factory-filled cups? For that matter, do the Catholic laity even get to drink communion wine in the first place?)
Oh, and then there was that odd animated bit with the rabbit. If the film had had a couple other moments like that, it might have been part of the movie's "style", so to speak, but as it is, it's just an out-of-nowhere effect that just sort of sits there in the beginning of the film. (The spaceman shots are a recurring motif and thus sit on a parallel track of their own; the bunny isn't really in the same universe as those bits.)
I know I should try to focus on some aspects of the film that I *liked*, so, hmmm. The bit where the protagonist tries to smash the pastor's car's windows comes to mind. "Gashole", too. If I sat here a while longer, I could probably think of some more...