There is also a capability that seems to be totally overlooked in these discussions. The ability to have multiple authors contributing to the the same WP installation but having separate managament of posts and comments in the dashboard.
A lot of the issues with displaying posts are very easy to accomplish with clever theme files, but post and comment management on the back end is obviously geared towards a single author with multiple authors kind of hacked together as an afterthought (not unlike multiple users in Windows).
It's terrible to have to be so harsh in this criticism, but this is a weakness of WP that unfortunately works counter intuitively and could potentially draw users away to better-implemented engines with time.
A lot of the Multiblogging solutions suggested in these forums are overkill for situations where multiple authors want to share a single installation of wordpress for blogging on a common site.
A good solution would be to enforce real user roles and permissions in the back end. On the front-end, all the pieces are there for the appearance of a multi-blog within the framework of a single blog on a single domain (using existing template tags and techniques).