One cost people don't factor in is that of a tried-and-true support mechanism. If [a Microsoft] product fails, we have a single phone number we can call.
The migration path to anything but Microsoft would require a forklift overhaul.
We were tickled to death with Release Candidate 2.
Microsoft has stepped up to the plate in a way we've never seen before.
Beyond the next six months is when I think it will be hairy. That's when we start instituting group policy. For instance, some school districts may not have the bandwidth to handle group policy.