Except from my firewire not working properly, I have no issues with noise or screen (ok the screen is not perfectly even, but it's hardly noticeable).
It does get hot when your working the processor, but under normal conditions, the CPU usage stays very low.
Generally I'm very pleased with the computer. The battery life is great (I get about 4 hours at nearly full brightness, only got 2 hours from my 17" PowerBook).
And with Parellels you can run XP, FreeBSD, Linux, FreeBSD, etc... without having to reboot, and the performance is pretty great.
The one thing that I'm not entirely happy with about the new design, is the size of the power brick. It's about 50% bigger than the PowerBooks! If you're a mobile user than it can be a real pain. I just hope that the new power bricks are more reliable than the old ones (which only lasted 6-12 months).