The AspireRevo nettop I picked up for $200 has an Atom 230 and a NVidia Ion chipset in it, and has zero problems playing back 1080p video in XBMC for Linux... Honestly, I'd be more surprised if it didn't playback 1080p.

EDIT: I will say based on the fact they're supporting hardware decoding on Windows (and maybe Linux?), I'd much rather pick up an Ion-based nettop and install Boxee as a software app.