Does anybody have experience of running a single image of SL on hardware
which was not all bought at the same time? Ie, is it possible to buy
machines from people like Dell so that you know that you can buy a
machine in a years time that will be sufficiently identical that a
pxeboot and an rsync to the known image will bring the machine up? 

I'm familiar with doing this for the classic beowulf cluster, it's the
procurement over a period of time that I'm interested in. Does anybody
actually manage this? Obviously we can do it with Macs and OS X, I would
like to be able to do it with Scientific Linux too. I'm relatively
neutral with respect to a vendor like Dell or a home-built solution like
asus.

Thanks

John