OK, http://www.wurk.net is up. I'm using MU without vhosts, through manually created subdomains. Why? because I'm working on a 'closed' network where I stay in control of a finite number of blogs, rather than letting any user create their own blog.
I was originally running the network on multiple installations of WP single user, but keeping the single generic theme up to date for each individual blog (amongst other things) was turning into a nightmare.
All pretty easy now with MU.
It's also a slightly different way of using MU than yet another wordpress.com clone.
By the way, if anyone wants to contribute to the network, I'm looking for more bloggers ;o)