Maybe it helped to have my expectations in the gutter, but I actually kinda enjoyed it. Oh sure, there's plenty of problems. There's not enough action, and a very thin plot with some cliches and contrivances. What is there I found fun enough, though. Reynold has charisma that manages to carry the movie. The action sequences that are there are all pretty original and look great. The only weak link in the cast is Blake Lively. It's odd that, too, since she was great in The Town. Here she's just phoning it in.
The movie does focus almost entirely on Hal, instead of the Cop. If you've seen the trailers, you've pretty much seen everything that Sinestro, Kilowog, and Tomar Re do in the film. The rest of the Corp do absolutely nothing. I actually hope this gets a sequel. Now that the origin is out of the way, perhaps we can do a less Earth-bound story focusing more on the Corp as a whole. Maybe bring John Stewart and Guy Gardner into the mix?
As for the special effects, well, sometimes they work and sometimes they don't. I had reservations about the suit. On Earth it looks just fine. On Oa, it sometimes looks like Ryan Reynolds's disembodied head is floating on a CGI background. The constructs all look great, though, and are used pretty originally. I especially enjoyed Hal's solution to an out of control helicopter.
So yeah, in finale, I enjoyed it well enough despite its obvious flaws. For movies this summer that I've seen I would rank it ahead of On Stranger Tides, and behind Thor.
Oh, and don't get up to leave as soon as the credits start rolling. There's a small scene partway through that made me happy with nerd-glee. It's probably not hard to figure it out, as it's something we all wanted to see.