I really don't have any negatives about this game.
Even though Ubisoft puts out an AC title every year, they give enough new stuff that the game doesn't get repetitive. The use of bombs, the hook line, were all fun additions. I love the series and I can't wait to see what the next title will look like. But if you enjoy AC, you will enjoy this game. I probably play AC more than any other game since they have came out with a new title each of the last three years and I never get tired of the game.
I've been a big fan of the AC franchise ever since it came out and they seem to keep improving on the last. However, it seemed as though they are starting to run out of ideas because Revelations only really featured 1 new addition (bombs) and 2 very different side missions. One nice feature however was the 3D option. I recently bought a 3D TV, so I tried it out and I was quite surprised. It had a fair amount of depth and it really did add a bit extra to the game. It was a lot better than the 3D in Uncharted 3.
The first side mission is a tower defense type game where you need to set up your assassins in various locations on top of building as swarms of enemies try and break through. In theory, it seems like a nice idea, but it really is terrible and I did not like it at all.
Second was Desmond's missions - they were very Tetris-like if I had to compare it to anything, as you needed to put blocks/ramps down as you climbed parts of these buildings you were in. It was a bit strange and frustrating at the same time. I eventually finished all 5 of them, but it took awhile and it wasn't worth the effort by the end.
The addition of bombs are okay, but it wasn't really worth making a new game for. The multiplayer was similar to Brotherhood, but they added a few more features.
Overall, this was a very solid game. It features all the same good stuff that the previous AC games had, plus a few unique ones as well. Also, if you have a 3D TV then this game is worth trying out in 3D.