I made good experiences with MediaTomb. But even better IMHO (and more reliable) for streaming music is the UPnP plugin of Rhythmbox, turning Rhythmbox into a UPnP media server.

gmediaserver, from what I have experienced, doesn't allow multiple connections. So while you're streaming music you cannot browse folders or start another track. This can cause the client to hang until gmediaserver is finished with streaming and responds again. The same behavior can also be seen with ushare.

Rhythmbox also sorts by artist and album, so the size of the media library wouldn't be an issue.