I have one of the ATV HDMI streamers as well, and quite love it as a supplement to my TV package - of course being a big fan of Apple products in general has me drinking the kool-aid, I guess. The seamless and intuitive integration between iTunes, Netflix, etc, any A/V or photo content on home computer networks and even iDevices is very easy to get used to, although the too slick for its own good remote necessitates an anachronistically geeky search function.
While I shudder whenever I pick up the remotes for either my Denon AVR or Motorola HD Cable box (one wrong selection and it can get very confusing ), every time I use the Apple TV I wish for a few more instant access buttons.
Keep in mind that this category of device is probably a loss leader product, subsidized by the content subscriptions - even to watch "free" internet content requires a minimal data plan. They're great if don't have "conventional" TV service and can be happy with the offerings on Netflix & YouTube, etc.
The ATV outputs both full HDMI as well as Toslink SPDIF , while the Roku 2XS might appeal more to the gamer set