I have been blogging with Google's Blogger since June and have had a generally positive experience. Only issue I have had with the service has been the absence of RSS feeds instead of Atom. I don't care about yet another standards war.
But lately I have started to see performance problems with Blogger when accessing my blog administratively, creating new posts, and publishing updates to the blog.
I guess this is a sign of a blogger explosion, but I might have to investigate alternatives soon.
I especially want something with a Mac OS X application I can post from, but I just haven't had time to do the research yet.