Well... I'm getting the momentus XP 750GB. I currently have a 750GB (the slow 5400rpm) and use TM to a RAID 1 NAS. I'll use carbon copy to install it and keep the other drive for a while. Someone has to try it. With the warranty, I'll take the risk. Everything is backed up and if the drive takes a turn for the worst I have my old one to keep me going.
I'll report back after Xmas. I'll install sd28 (or the latest) and see what happens. If it lasts a couple years in time for SSD's with high capacity to become commonplace and economically feasible it may just work out. I'm not willing to give up the optical drive since I watch DVD's.
Thanks for all the replies and even the negative viewpoint firsthand. It made me rethink things, but I think it's worth a shot. Someone has to put forth the risk and become a guinea pig for tech support.