It seems strange to me that the devs would start the huge project of creating TBC servers when their vanilla servers aren't in perfect working order yet. I check their twitter feed every day to see what they're working on, hoping that they'll announce bug fixes or cluster development progress, and I'm always disappointed to see they're instead working on an entirely unrelated project. Take the windfury bug, for instance. That's an incredibly game changing bug for a shaman player, and yet it's been completely ignored for months, even though it seems like it would be a much smaller task to fix than adding an expansion server would be.
Fixing the lag at peak times and the numerous bugs should be the top priority in my opinion. For the players with A.D.D, who will never be satisfied with any version of wow ,as they constantly want something fresh and different, the preferred path of development would be to just pump out as much content as fast as possible without regard for the quality of gameplay. To the players like me, who came here for a quality, blizzlike vanilla server, having a flawless version of vanilla would be far better than having a flawed version of vanilla + a flawed version of tbc.
As always I appreciate the good work Nostalrius devs do, but I don't agree with starting a huge project like TBC while there's still major problems with the vanilla server.