´´2) is there any serious Bugs? are there any closed instances? (i mean instances that should be in TBC/vanilla, WOTLK is not out yet)´´
If we are talking about raids, not even single 1 is working corectly.
Archimonde in Hyjal is bugged like hell, even after fixing him.
Before, he was doing nothing.
After ´´fixes´´ they made him practicaly impossible to kill by incrasing his hit points double and making his abbilities insane... including zero hitbox.
Black Temple and Sunwell are closed at all.
In Tempest Keep Al´ar is bugged like hell as well, but at least possible to kill.
Kael´thas is closed.
So, only thing you can enjoy in pve are T4 and T5 raids, which are opened.