I just thought I'd check back in with an update. I've been using the free Twonkyvision Music Server v2.8 for a week now. Everything seems to be working fine with my Linksys WMLS11B.
Now, the only problem is the Linksys is so slow paging through a list of thousand of albums, three at a time. I might upgrade to the full Media Server for the $18 bucks (or whatever 15 Euros equals - I can't remember). The Media Server gives more options for the directory tree structure (ie: genre/artist/album instead of just by artist or by album). Tonight, I wanted to listen to an album in the Ms and it would have been a lot quicker to get up, go find the cd and play it!
I'm also thinking about looking into the Apples Airtunes thing, since I do most of my library maintenance stuff in iTunes. I find its browing, smart playlists, etc. to be better than musicmatch. If only iTunes could serve uPnP, I'd have it made.