Had mine since release day.
Thoughts:
Build quality. Very good. The machine feels completely solid. In comparison, the Dells and Compaqs we have sitting around the office seem to be comprised of flimsy plastic and empty space.
Awesome screen. Did a manual calibration and it's very pretty. Glare is no worse than what I'm used to from my CRT at home.
Keyboard. Awesome. Feels surprisingly nice to type on, especially given the fuss everyone's made about it. Good feedback, good spacing. Am a little concerned about getting gunk under the keys, but all things considered the risk isn't much higher than with a standard notebook keyboard.
Very quick, both in MacOS and Windows.
Get more RAM. I haven't used the machine with 512 but it flies with 2GB.
Heat. It gets warm. Not bake-your-nads warm, but okay-I'm-starting-to-sweat-a-little warm. Haven't had any incidents of egg-fry level heat, as some people reported with the MacBook Pros. I watched two 45 minute episodes of House, reclined with the notebook on my lap, and was never uncomfortable. Might be considered pleasant come winter.
Weight. It's small, but it's dense. Weighs more than you would expect (to the point that the first thing everyone at work said when they picked it up was 'Whoa. It's heavy.'). That said, it's pretty light in absolute terms.
Sound. Speakers sound good, but the volume level sucks. Bring headphones.
Haven't really encountered any major problems with it. Had some trouble seeing my PC at home over the wireless network, but it turned out that was because I wasn't sharing the HD.
Once a couple of days ago my friend put it back into its (thick, insulated) sleeve before it had shut down. Something went wrong and the machine kept running as if it were open. When I pulled it out two hours later it was HOT. Like, fans blowing, processor whining, MBP-esque hot. Plugged it into the wall and let it cool off overnight and it was back to normal the next morning. Still haven't figured out what happened there.
Anyway, happy owner. I'd recommend getting AppleCare if you have any Rev A concerns.