Bla has given me the approval to start it up! If you have an opinion, then I guess say it here. I'll probably look into setting it up sometime in the next 2 days. We'll have this going until 1.6 is out on Bukkit.
Some information:
http://feed-the-beast.com/ - Official mod pack site
http://feed-the-beast.wikia.com/wiki/Feed_The_Beast_Wiki - Unofficial wiki (a lot of useful information)
We'd probably be going with the MindCrack modpack, mostly because it is the one designed for larger servers and has a bunch of fool proof and lagbusting mods.
The biggest question is - GregTech?
Basically it is IC2 on steroids. It makes all the IC2 recipes harder and more expensive, however also adds a whole ton of depth to the mod. The debate is pretty big, but in FTB there are so many ways to get materials, that I see no reason why to not have it on.
I will also implement one rule -
In FTB you can have chunk loaders and machines that easily produce thousands of entities, which will kill the server. Multiple offenses of this WILL RESULT in a ban UNTIL the FTB server is done! Do your research before you kill the server!