I said I'd do it, so I done it.
That's an Acer Aspire One (1.5GB RAM, 120GB HD) running OS X 10.5.4. (iPhone included for scale. Sloppy room in background because I wasn't policing the kids while installing OS X). I have Airport, MobileMe, 1024 x 600 Quartz Extreme video, audio, pretty much everything, in a 2 lb package. No CD/DVD, of course, without a drive! Sleep doesn't work and Bonjour is iffy. Can't mount my iDisk, either. Everything else just works. Dual boots with Windows XP Home.
Initial setup was involved, but it was well documented. The hardest part for me was disassembling the machine to upgrade the RAM and swap out the provided Atheros wireless card with a Dell 1390 card from eBay.