Have used it a bit on a hacked Apple TV. Reasonable software but I was using the alpha as the new beta version didn't run on an ATV (until today, actually, just after I "un-hacked" my ATV. Oh Well.) You can use it to get BBC iPlayer on your TV as well as other things (and your own content, of course) but there are increasing ways of getting the iPlayer coming on stream.

Getting content to your TV is starting to move out of the geek realm and into the mainstream, but it's still early days, especially in this country, where we seem to be a little behind the States, and I found the online content quite limited by that.