I have a special SD card made up that has all of the correct boot configs set and a small script to update everything and set up the Pi for PXE boot. After everything is configured, I take out the SD card and let it just pull boot images over the network. My main home server serves everything up over tftp. The only downside is that you can't get this to work over wifi. The wifi Pis get read only SD cards that are all configured the same so it's easy to reimage a new one if the card dies.