I use Radio and like it for the most part.  What I don't like is its tendency to depend too much on UserLand servers.  I don't mind generated pages with static resources from busy servers (i.e. W3C, UserLand), because I can replace them with my own copies.  What I am concerned about are dynamic contents pulled from UserLand servers, particularly the comments.

UserLand servers are usually dependable and speedy, but occasionally they are not available (like now).  When Radio comment service is down readers can't access the comments.  Once posted, comments are static content which can be stored locally as XML and HTML files as well as being embedded in RSS files.  Only the comment posting service need to be handled by UserLand servers since many Radio sites don't have CGI capabilities.