I'm going through and finding things that bug me. What do you expect? I'm a cranky old man. So, here they are as I discover them.
1. Using Malefic and Sanctic powers in inappropriate armies, such as Space Marines summoning daemons or Chaos Sorcerers banishing them. This is not only out of character but possibly game breaking. After all, if your super cool character is about to die, why NOT replace them with a free Greater Daemon?
2. Different weapons in the shooting phase are now resolved completely before the next weapon type goes. So, if you have nine boltguns and a meltagun, and an enemy unit has one model 11" away, use the meltagun first. If you kill that guy with the boltguns, the meltagun no longer has range, EVEN THOUGH IT SAYS EARLIER THAT ALL GUNS FROM A UNIT FIRE SIMULTANEOUSLY.
3. Models with two pistols can fire both! I'm listing this here because it's so rare. Seraphim come with two pistols standard. Cypher has a special rule to let him fire both pistols. Will this lead to double-plasma-pistol sergeants? Probably not because that's 30pts but still that's silly.
4. Still random charge UGH. However, difficult terrain is now just -2" which makes charging through difficult terrain an actual viable option rather than a really crappy one.
5. The rumors that you can consolidate into close combat like in 3rd edition were false. I'm not sure it's fair to complain about a rumor but I'm doing it anyway because Tau are unstoppable right now and close combat in 6th was a joke.
6. All missions have Mysterious Objectives. Unless both players agree not to use them, more random crap will happen every time you touch an objective. None of them are REALLY bad, even the worst one causes some S4 hits. But it's just more random stuff, and you know how I feel about that.
Wow, that's actually a short list. Basically, if an opponent doesn't abuse Malefic or Sanctic and doesn't want Mysterious Objectives, this is just 6th with better charge rules and more organized psychic rules. Who knows? 7th could be awesome!