Well, I waited 20+ years and I'm going to put my 2 cents in like everyone else. Warning... this is a long post and has a lot of nit-picking in it and a LOT of spoilers.
TL: DR version upfront : Decent movie that was to long with a lot of wasted potential.
Dialogue : Terrible. There were a lot of unnecessary lines that just made me roll my eyes. It seemed as if the script assumed the audience understood NOTHING and needed some "yuck yuck" lines for laughs.
Pacing : Why throw everything I wanted to see up front and then give me nothing but metaphysical junk filler until the ending? The disc wars and light cycles should have been seperated by more than CLU meeting Sam. TRON (original) was a flawed movie for sure, but I think the pacing was much better.
Something is nothing : Flynn's light cycle, the tanks, Rinzler's sudden epiphany, programs seeing Flynn as a god... these were all alluded to, but never realized. I'd like to have seen the tanks shell the crap out of the EOL club. I'd like to have seen "the fastest thing on the grid" be just that. What prompted Rinzler to redeem himself? We get a glimpse at the resistance and how programs view Flynn at the EOL club... briefly.
Overall plot : I don't buy it and I think it's to "out there" even for a movie about people being inside a computer. Someone earlier mentioned the Matrix and that's exactly how I feel about the story here. It's to complex and unnecessary.
Summary : I didn't hate the movie and thought it was alright. The visuals were fantastic, the action was pretty tight overall and the parts that worked, worked really well.
Extra mention : While young Flynn was "off", I thought it was a solid effort and didn't detract from the movie for me.
EDITED : Removed the spiritual bit because I didn't complete the sentence and can't remember what my train of thought was.