I put Gutsy Gibbon on my new MacBook today. It rocks. My external (23") monitor works nearly flawlessly, and the open-source Intel drivers worked out of the box to give shiny desktop effects!
I first installed ReFIT, then I used diskutil resizeVolume under Mac OS X to resize my hard drive, and then I installed Ubuntu into the empty space. It couldn't have been simpler (now that Boot Camp is no longer free from Apple). My monitor works with the Intel drivers, and I use xrandr to configure it on-the-fly because I often move my computer. The screen still goes crazy occasionally, but it's survivable.
Anyway, I highly recommend people try it. MacBooks seem to take Ubuntu very well! I have nothing to complain about at this stage.