I installed Windows 7 RC on my little HP Mini netbook at the weekend. Installation went smoothly, with most drivers working (except internal mic, oddly enough). Added it to the work domain today - very smoothly & easily. Work's security software hasn't caught up with it yet, so I've got a free one until it does, but other than that I have to say, as a hardened Microsoft sceptic, I'm thoroughly impressed.
It's really quite fast. The XP Home that was factory installed on the netbook was ok. I installed XP Pro on it for work, and it slowed a fair bit, especially with security software too. Still tolerable, though - it only slowed when I was flitting between apps that were each working (ie. XP's no multi-threading).
Windows 7 is fast, even on a netbook. It boots, with domain user login, in under a minute. I've had no pauses when flitting between apps. The Aero preview screens work and move sweetly. It sleeps and wakes in under 10 seconds. It feels light and breezy, but also robust, diagnosing some network connectivity issues very well.
Better than Apple OS X? In terms of usability its just about on par, but OS X just looks more stylish and is usually in a more stylish box with naturally better integration. The startling feat that Microsoft have done is to make this work so well on a non-native, non-'certified' machine.
I hate to say it, but: bravo guys. At the end of the age of the desktop OS, Microsoft have created one excellent last hurrah.