I haven't tried the iPad/Android control as my wireless keyboard is always close by but I know you can do it via apps like this. Official XBMC Remote - Android
XBMC supports FLAC and just about every other format you can think of. With HDMI or optical out from your PC, you can send the uncompressed music, digitally, to your receiver or pre-pro without worrying that your sound card isn't maybe 'good enough'.
So yes. it is excellent as a tool to plant your butt in the sweet spot and use it as a very easy to use graphical menu to listen to your music library.
Reread your post and I notice you mentioned "stream". I store my music library on my HTPC that is hooked directly into my AV receiver, so technically, I'm not using it for streaming.
However, I know it is NAS, UPnP and AirPlay compatible. I don't know the details as I never had the need. However, the documentation on thier web page is quiet good if you want to look deeper.