The AppleTV works fine for me getting my media on there for the most part. All I did was rip my DVDs to an industry standard codec (H.264) or have eyeTV encode to it, and added them in iTunes. Your milage may vary when using certain, umm, acquired formats that someone else encoded to some popular, but not standard codec. :-P

Overall, my primary use of Boxee in the past was to watch online streamed shows from Hulu and other sources. That really didn't work well on the AppleTV (lack of CPU power to deal with Flash, Hulu trying to actively block Boxee).