We switched from one CC3 network and one vanila (with no gpo's!!) to one single network with 4 new servers just over a year ago and it was the best thing we ever did!!! It makes our lives so much easier.
@alonebfg- we have got 2 address ranges as well but when we migrated networks we bought an ISA server that only gives out one address to our LEA network and use 192.168 internally now and again this works well. Although i am having to set up a few machines with bypass' on the ISA server as we have got a new filtering system and it requires a specific address to unblock certain machines from more websites.