I came back here few weeks ago after leaving the server for almost a year.
The changes are very good so far, many fixes for crucial bugs have been implemented and the game is much more stable right now.
However, there is some delay in queue for bgs/arenas (horde side,) I remember before leaving it was instant queues on most times of the day, that's probably because we lost many players!
But, I see that a lot of players are coming back and that new players (including gladiators from retail) have joined the server, which is good for the community.
Also, MoP PvE content is almost completely fixed and PvP seems fine to me at the moment.
That's in short. ;)