I have mine setup on my iPad only, but to stream movies and shows from my computer when I want to lay in bed for instance and watch. I also have XBMC on my AppleTV, but that is so I can get things like 1channel, icefilms, tv network plugins, etc. to watch shows and movies.
There are definitely lots of other uses and I'm sure others will chime in with what they use it for.
I personally wouldn't bother. While up to, say, a year ago I would have said it was by far the best player for iOS, that's no longer the case, unless you need DTS or Lossless WMA support. Its SMB streaming support is particularly buggy and the player is, generally, slow on the iPad 3, compared to the latest best AppStore players.
All in all, don't bother - if you don't mind paying for some AppStore players, get nPlayer. You'll love it. AVPlayerHD is also great but I'd take a look at nPlayer first - it supports networking and subtitles better. The JB'n, free(!) RushPlayer+ is also much better in some respects.