Our deployment consists of about 5000 laptops and desktops supported by one JSS and three replicated servers for imaging and package deployment. The only issue I have is that when the database grew that big, my web interface struggles with loading the full list of computers (like when I create new or edit existing static computer groups) As far as I am concerned, as our system grew, computer management stayed the same and in many cases became easier.
Our deployed computers consist of everything from Mac OS X 10.3.9 tear-drop iMacs and iBooks to dual processor Power Macs to brand new 10.7 MacBook Pro's.
The largest deployment (in this case redeployment) we have done was over last summer when we imaged about 1000 laptops (MacBooks and ibooks) and sent them back to the schools. Our biggest success was in prestage imaging. That allowed one or two of us to set up all of the policies and preferences and the rest of us just plugged in and kicked off imaging. The part that was less exciting was our iBooks would net boot, but were painfully slow in connecting and imaging, so we supplemented with external hard drive imaging.
With iOS devices, from what I can see, setting up your configuration profiles and VPP with Apple for applications before iPads start rolling in is a must. There are more people here that have more experience with iPad/iPod deployment, so I will leave it at that
