So far the positives have outwighed the negatives, based on the few things I have read from reviews. I, like many others, don't want spoilers...but I carefully read a few snippets from the negative ones, and this is what I have gathered with no spoilers:
1. This is more like Batman Begins, than The Dark Knight. So if you liked Batman Begins, or if you were part of the group that enjoyed Batman Begins more than TDK, you will love this movie. If you liked both BB and TDK, this prob won't beat out TDK in your opinion as the best movie, but you will still like it.
(summed up from the IGN review that wasn't really negative, but this was something he mentioned)
2. Bane doesn't grab your attention when on screen as much as the Joker did. He isn't as charismatic.
(personally I think they are 2 completely different characters, so to compare him to the Joker doesn't really make sense. Hardy even said in an interview months ago that Bane is not like the Joker, he is all about brute force, not showmanship etc.)
3. It's too long/bloated, and it takes a good hour to get going.
(Once again, if you are a fan of the series so far, why would you care how long it is? TDK was only 10 min. shorter than this, and I sat through it 4 times in theatres and always wanted more. This being the last one, I want as much as we can get. Also about the taking an hour to get going, to me that makes me think they take a good time with things and have a good buildup to things. That it tells a story rather than just action. Considering an hour of buildupm then that's an hour and 45 minutes of payoff...that's as long as a normal movie. Which I am very ok with.)
4. Bane is hard to hear.
(Said by a reviewer who saw it with his 21 year old son, and he too said he couldn't understand him. Personally I have never had a hard time understanding him, even in the very first trailers where others had trouble understanding him. Also, I will note that this was the only review where this was mentioned...so it could just be a problem with the viewer rather than the movie.)
5. It doesn't live up to the hype/isn't as good as TDK.
(This was from Christy Lemire's negative review. She was disappointed by the film and most of it was based on the fact that it wasn't as good as what she expected it to be and didn't live up to how crazy the hype was. Admittedly she said she didn't like Begins. She was a huge fan of Heath's Joker, but didn't find Bane as sexy or charismatic here. So take it for what it's worth.)
These are the complaints I gathered from the few negative reviews that are out there. Personally, none of these complaints are things I am worried about, nor are they things I usually complain about a movie.