The folks at AnandTech reviewed two IONs which, due to XBMC’s VDPAU support, make decent platforms for cheap linux based HTPCs capable of playing HD content.
A section which you might of particular interest is titled Ion Meets Linux: XBMC:
What impressed me most about the XBMC experience on Ion was how easy it was to setup and how fast the interface was. Obviously we’re still quite limited by the Atom processor, but this thing felt much quicker than when I tried MCE Video Browser on the Ion earlier this year. It didn’t actually feel sluggish; I saw some choppy transitions at times but it was totally usable. Not to mention much better than most UIs on traditional CE devices.
If you’re looking for a way to stream content to your TV, I’d strongly recommend giving XBMC a try on the Ion. It works very well and delivers a clean, easy to setup, easy to use HTPC experience that’s fully hardware accelerated by NVIDIA’s Ion.