Its hard to find really good quality GM/GS soundfont sets anymore, but they are around. Here are some I know about, some free, some not.

NAProGM.sf2 Included with Notability Demo.

Ntonyx freebie soundfont: http://www.ntonyx.com/sf_f.htm

Ntonyx commercial soundfonts: http://www.ntonyx.com/sf.htm

http://soundfonts.homemusician.net/collections_soundfonts/airfont_340.html

http://soundfonts.homemusician.net/collections_soundfonts/fluid_release_3.html

http://packages.debian.org/search?keywords=fluid-soundfont-gm

http://www.schristiancollins.com/generaluser.php

Here is a related thread too:
http://www.kvraudio.com/forum/viewtopic.php?t=24876

I guess BIAB is trying to move to RealTracks, which are really outstanding, but many styles still require some midi sounds and they could drastically improve the sound quality by either making it possible for us to select which DLS soundbank to use, and/or them providing us with a nice SF2 also to load in there.