did you see that it is out of beta mode now? it is now officially infused v 2.0.0, and can be downloaded from GTG's section in ROM manager and flashed normally!
but i'd still go to his XDA page, and follow his directions precisely.
but yeah, Ed, sounds like you have something wrong... maybe it isn't the phone, but rather, just a bad battery? it sounds like you have connections at samsung, since you got to play with that SGSII... so can you maybe swap batteries for a day, and see if that's it?
the battery life should not be crap... if you just go to the last page of the XDA thread, and page back, you will see many reports stating that the battery life is incredible!
good luck, and don't give up on the infuse! unless you're gonna get the SGSII... haha