Microsoft is getting ready to roll out Vista and I really can't think of any good reason to upgrade.
There are 6 different versions to choose from, so it's not immediately clear to me which one is most suitable. Then there also seems to be a pretty draconian license agreement that should put most people off.
Perhaps if I bought a new machine (and actually I'd have to have the latest hardware to be able to run the beast considering its requirements) and had Vista pre-installed then I might just keep it. I think this reason, rather than anything positively attractive, is going to be why most future Vista owners will have this product. Incidentally, if you do buy a new machine but decide that you don't want Vista (or any previous incarnation of Windows) you can decline the User Agreement and get cash.
for the "Most user friendly distribution." It's stable, fast, secure (well, much more than Windows is) and free!