I'm doing it for he achievements. And the pets.

You keep your ranks, and you keep your seals. I dunno about barding yet, but I'm assuming that is also frozen.

You can change GCs every 30 days (or something like that), so it's not like it's so hard to go back to your original one if you want. I'm just getting this over with so I can be back in my original GC for PVP.