I've got XBMC on my AppleTV and it's worth having for the visualizer alone (I cannot understand why Apple hasn't added one yet after all this time and all the new ones in iTunes, which run fine on my old PowerMac even). However, I'm finding that the picture viewer is pretty much worthless since it refuses to show all my pictures. I added several SMB shares for all my photos on my PowerMac server and a LOT of photos simply will not display period. It'll show the filename, but no image shows up. Other images show up fine and there is no rhyme or reason to it that I can see. I might have a single directory that has 50 photos in it and maybe 20 won't display or maybe 40 won't display or maybe just 10. Sometimes none will display. The only reference I've seen to this problem with a Google search is for XBMC 1.0 from like 2005. The developers said they'd look into it and the thread pretty much just ends with no resolution listed. I can find no other mentions of this issue yet there it is just like that thread described in XBMC for AppleTV four years later.
Oddly, the primary photo directories I use to display with AppleTV also seem to show up OK. It's the directories I do NOT use on AppleTV that seem to have problems. There's nothing wrong with these photos. I simply don't normally display them on AppleTV. For the most part the ones I do display with AppleTV are my own photos from vacations and photo albums and the like. The ones I don't normally display pictures I've downloaded from the Internet (e.g. swimsuit pictures, etc., which I don't want showing up in my screensaver or photo lists when I have guests over, but which I might want to view on my 93" screen once in awhile and so XBMC would seem to solve the issue for me since I can use it to browse straight off the network SMB shares instead of locally stored photos, BUT if they won't display it's not very useful at all)
XBMC shows WMA movies just fine, although sometimes it takes a few frames before the picture clears up for some reason. M4V movies play OK too, but it doesn't read the embedded movie information so I had to painstakenly correct all its "name" based guesses to get a useful list out of it, which I'm afraid will end up getting erased when Apple updates it again. I guess I should back it up with SSH or something. It's too bad they don't just read the standard tags. That's what they're there for and what I spent hours using MetaX to accomplish only to have XBMC just ignore it all including such basic things as chapter markers. It will at least recognize multiple soundtracks. But I still use AppleTV's own interface for watching movies most of the time due to this oversight. Fortunately, for music, iTunes already organizes music by artist/album/track so it's not bad selecting songs through the regular directory structure (XBMC will not read the iTunes server lists, only SMB shared directories unless they're stored locally on the Apple TV...what's the point in that? The whole point in having Apple TV is to STREAM everything to it from a server of some kind.)
Basically, XBMC has a long way to go to replace Apple's intuitive interface, IMO (and even that could be greatly improved with iTunes Store style lists for your own movies, etc.). Simply adding codecs to the primary interface solves most issues, though.
I also tried Boxee, but it's DOG SLOW overall (at least while it's indexing everything which takes literally forever) and Hulu runs like molasses on it. Despite being encoded in H264 480P, it runs like it's trying to load 1080P (i.e. skips frames like mad). Maybe that's due to it indexing in the background or something, but if so you'd think it'd be smart enough to NOT do that crap while I'm using it. Index while I'm sleeping or something. If it's not that then it's just a crappy program (at least for Apple TV use) because no one wants to watch mere 480p Hulu shows at 12fps.
Oddly, the primary photo directories I use to display with AppleTV also seem to show up OK. It's the directories I do NOT use on AppleTV that seem to have problems. There's nothing wrong with these photos. I simply don't normally display them on AppleTV. For the most part the ones I do display with AppleTV are my own photos from vacations and photo albums and the like. The ones I don't normally display pictures I've downloaded from the Internet (e.g. swimsuit pictures, etc., which I don't want showing up in my screensaver or photo lists when I have guests over, but which I might want to view on my 93" screen once in awhile and so XBMC would seem to solve the issue for me since I can use it to browse straight off the network SMB shares instead of locally stored photos, BUT if they won't display it's not very useful at all)
XBMC shows WMA movies just fine, although sometimes it takes a few frames before the picture clears up for some reason. M4V movies play OK too, but it doesn't read the embedded movie information so I had to painstakenly correct all its "name" based guesses to get a useful list out of it, which I'm afraid will end up getting erased when Apple updates it again. I guess I should back it up with SSH or something. It's too bad they don't just read the standard tags. That's what they're there for and what I spent hours using MetaX to accomplish only to have XBMC just ignore it all including such basic things as chapter markers. It will at least recognize multiple soundtracks. But I still use AppleTV's own interface for watching movies most of the time due to this oversight. Fortunately, for music, iTunes already organizes music by artist/album/track so it's not bad selecting songs through the regular directory structure (XBMC will not read the iTunes server lists, only SMB shared directories unless they're stored locally on the Apple TV...what's the point in that? The whole point in having Apple TV is to STREAM everything to it from a server of some kind.)
Basically, XBMC has a long way to go to replace Apple's intuitive interface, IMO (and even that could be greatly improved with iTunes Store style lists for your own movies, etc.). Simply adding codecs to the primary interface solves most issues, though.
I also tried Boxee, but it's DOG SLOW overall (at least while it's indexing everything which takes literally forever) and Hulu runs like molasses on it. Despite being encoded in H264 480P, it runs like it's trying to load 1080P (i.e. skips frames like mad). Maybe that's due to it indexing in the background or something, but if so you'd think it'd be smart enough to NOT do that crap while I'm using it. Index while I'm sleeping or something. If it's not that then it's just a crappy program (at least for Apple TV use) because no one wants to watch mere 480p Hulu shows at 12fps.