You said:
"If you try and put a generic firmware on it, they will probably penalize you and re-push their firmware back down to the device.
This is what they did with the SideKick, ..."

They do however host a forum on their web-site, which seems to be devoted to hacking Android on the T-Mo phones.
http://forums.t-mobile.com/tmbl/boar....id=AndroidDev