Thanks for the answer.. I guess I didn't think too hard on that old hardware bit but I'm sure there's plenty of peripherals and hardware RAID cards that might fall into that category. I don't know about you but I'm not keen about replacing hardware if it's not broke and works for it's intended purpose. /shrug. Anyhow its suffice to say that you need fairly fresh hardware for new software. I get that.
We're talking semantics though. I guess my question really was - Is driver support for the 64bit kernel more backward compatible then say the MS world? I'd hope yes considering MS loves to play the driver/support card to force upgrades.