Deploy Studio is a wonderful piece of software that lets you make a system image from a Mac and then deploy it to loads of other Macs from your Mac server. I’ve just upgraded 16 iMacs to Lion like this, taking only about 10 minutes per machine (perhaps 20 minutes per machine if you’re doing 5 at the same time). All you have to do is netboot (hold down ‘N’ when you turn on the Mac), which makes the computer boot up from Deploy Studio on the server. Then you choose the image you want to deploy, and then it does it all for you. Marvellous. It even automatically binds it to the relevant directories as well.
And with gigabit ethernet, this process really is much faster that it used to (possibly even 10x!).
Toucan set this up for us, of which I am very appreciative.