I would like to add my vote in favour of there being a fixed set of packages (I mean including the base) which constitutes the most recent "release" or "version" of Debian. This is so that new users can go to a specific place and get a set of packages which are quasi-guaranteed to produce a working system. (The current continual evolution does not often lead to incompatibilities/new problems, but it can.) Clearly the release should not be defined by imposing a cut-off on an arbitrary date, but by deciding that a suitable level of functionality has been reached, and then taking some time to clean up any bugs that remain. Probably someone/some group has to be responsible for deciding what needs to be fixed, chasing this up and deciding when the release is ready.
I also believe that for the public face of Debian (and otherwise) it would be useful to be able to refer to a specific "release" and for that to mean a well-defined set of packages. (Otherwise any numbering scheme does not have the conventional meaning at all.) Certainly some provision has to be made for important bugs (maybe just security problems?) discovered after the release. I do not know whether it is preferrable to replace the relevant packages in the release, or to make the fixed versions available in some well-documented place, though I lean towards the latter. The latest packages should also be available of course. I very much appreciate the ease of installing/updating Debian packages, and I believe new users will find out for themselves fairly quickly how easy it is.
