This news is really late, and is this really more important that the news that the Linux client for L4D2 and steam releases at the same time as workshop?
Just built my Gaming PC around 4 months ago, I had this on XBOX when I had it, traded it in as I have my PS3, and out of the two is my favorite. Looks like I might have to buy it back again to try some of the MODS, will be the first mods I use! I do think that steam should support this kind of stuff more, as I like the idea of mods but don't want to risk downloading badly coded or worse malware.