On the Script Meridian mailing list, Bill Kearney showed that Netcraft is already counting a bunch of EditThisPage, Weblogger, and Weblogs.com sites as separate UserLand servers. He estimates that Netcraft has found around 270 unique IP addresses using Frontier to serve content.
Netcraft's list of Userland servers is worth nosing around to find interesting sites. One: Author Power, a support community for freelancers who write for the ZATZ magazines Domino Power, Palm Power and Palm Power Enterprise. Another: Chocophile, a community for "connoisseurs of chocolate."