I finally got my own experience with Windows Vista Ultimate over the last few weeks, having been somewhat forced to downgrade from Vista Home Premium 64 bit back to a 32 bit based version of Vista to get some software that just wasn't cooperative to behave itself (DVD playback software if you must know, which I'm still less than impressed with since the makers of same have had time to get their act together and make their products compatible with 64 bit Vista).

When making the switch I had a 32 bit copy of Vista Ultimate available or I could go through loading up Vista Home Premium but in 32 bit instead of 64 bit.  I figured what the heck, use the copy of Vista Ultimate and save the copy of Vista Home Premium 64 bit for loading on different hardware later (it wasn't an OEM version so I could transfer it around later if I wanted).