I watched it today with some friends. It's not nearly as terrible as I remember. I think a lot of the negativity towards it is so blown out of proportion. Up until Shinzon kidnaps Picard and tells him he's "lonely" I think it's a very compelling and interesting Star Trek movie.
Once we find out Shinzon's plan and his motivation, I think the movie begins to fall apart a little. Additionally, there's something about the movie where the whole affair feels almost tired. I can't explain it. It almost feels like the film is an early draft of a script.
In the end, I don't hate the movie. If anything, I get frustrated with it because it could have been so much more.