Updating a large number of hosts from a binary repository

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I would like starting to use pkgsrc on some hundred Linux clients.

Assume I have a bootstrap and a list of desired packages and their dependencies 
installed.
Now comes the next quartely release. I prepare binary packages on a server and 
optionally update the list of packages I want installed on the clients.

Then, what's the most appropriate tool so that, after some minutes of 
inconsistency and un-usability of the clients, I have:
1. The most recent versions of my primary packages installed/updated
2. The most recent versions of all dependencies (no matter whether the package 
they depend on has been updated or not)
3. Preferrably have the dependencies marked as such (i.e. AUTOMATIC=yes)
4. Optionally have all outdated/no-longer-used packages removed.

The tricky part seems to be that even if appfoo doesn't get touched at all or 
is still happy with libbar-1.0 from the old release, I want libbar-1.1 from the 
curent release installed.

My impression is that there are more tools aiming at this then I have time to 
evaluate, so any help (preferrably from the real world) is welcome.