Unfortunately no x64 support as of yet, but i did like it on XP 32, it was nice to know that i had one app to 'take care' of my system, also many users will find the backup features new and interesting.
My only gripes with onecare on xp were that when it found a nasty it wouldn't tell me more information about it or let me view it's folder location (co-incidentally it never actually removed it properly kept coming back yet no other AV's or AS's picked it up), this may have just been a one off, an error, a false positive or a known issue
NOT that my last paragraph should put you off using it, its a great first time effort from Microsoft, and I'm sure it will prove to be successful as more and more people visits the shops to buy a new computer and software, I was really impressed to see a good Microsoft Software display in some shops in the UK easily listing the differences between Vista Versions, Office 2007 versions and also having OneCare in the same display, Struck me as an easy to understand All-in-one Start up selection for a brand new PC
lets hope 1.6 < includes x64 support