bit late I know, and I hope the iMac is going well
I use iMacs at work and have a MacBok Pro at home, all running BootCamp with Windows XP Pro SP3 on them, I would not touch Vista with a barge pole atm!! XP runs smoothly on them and I have had more problems with the Dell PCs with XP on them and none on the Macs!!
I know this always seems to be the answer that Mac people give, but 'it just works'!!
Just remember that whilst you are running windows, your computer is no longer Apple, and is now open to all the nasties that plague the PC world
PointonsTache