I guess it can be good for using Creative ALchemy which allows you to run DirectSound3D games on Windows Vista and W7 with full hardware accelerated 3D Audio and EAX support. I'm on Windows 7 now (it's been a very recent change, I've been using Vista for four years or so until that move) and I haven't yet installed most of my games but I remember using Creative Alchemy for Diablo II, Star Wars: Empire at War and I believe it was Star Wars: Galactic Battlegrounds as well (can't recall clearly).
As far as the sound quality goes I think that on-board audio in most of today's motherboards is good enough. I've used the on-board audio from my ASUS P8P67 Pro's Realtek ALC for a few days and honestly I don't remember being disappointed by the audio quality it provided for most games, although I don't think I listened to any music when I used it. The only potential "problem" I can think of is perhaps that some on-board audio would be limited to lower number of maximum-supported channels, like having only 8, or 16 audio channels when a game for example would have options for 32, 64 or 128 channels which a dedicated audio card could support.