I have been dabbling with it but time isn't on my side. So far, I've only managed to reverse engineer wq_town from beta 1.2 into a bsp file that I could then open in radiant.
IF I HAVE TIME, I plan to convert this map for beta 2.0 (only to be released with ICI's permission of course.)
IF that is successful, and
IF I can find the time, I'd like to try making my own original map for 2.0
I've asked my brother, who is an experienced mapper, to do something for WQ3 but he doesn't seem very excited about doing it so I'm not holding my breath.
I'm trying but don't expect anything from me very soon.

I want to make a quality map and not some crap so this could take me awhile.
Setting up radiant for this mod isn't what I would call easy. See
this thread for an idea of what I've been going through.