I got the PS3 primarily for Blu-ray playback (and the fact that it's a better sd-dvd upconverter than my standalone.. heh).
(Ab)use the Playstation Store for the free trailers and demos.
Threw my CDs onto it as aac, but mp3 < aac < (FLAC, damnit!).
Not too into the gaming thing, but I play for a bit now and again. Lego Star Wars is the best home theater game ever.