I just downloaded Radio Userland and decided to try it out. I've used Slashcode to build a number of community based sites, including one for the course I teach at Brigham Young University on enterprise computing and one for alumni of the Japan Tokyo South Mission.
Originally, I'd thought I might use Slash to build a weblog, since I'm familiar with it, but it seems just slightly different than a tool for building a weblog since its based on communities. In fact, as I explored some, I had the thought that what RSS and weblogs do in a decentralized fashion is similar to what Slash tries to do in a more centralized fashion. Still for things like my course, I'd have to concede that I'd have a tough time getting 45 students to all get set up on weblogs and then get them all connected together through RSS. Maybe all students will need to have a weblog for posting assignments, etc. someday, but I'm not quite there yet.