An interesting dynamic is certainly forming. I see many MS types becoming more and more interested in Linux all the time. Attitudes are changing, and that is in no small part due to the impression that the IT grunts are coming away with when they see the price of the new Vista licenses. MS is in desperate need of a reality check. I'm an MCSE, and just recently bought the courseware for Linux+. Though Linux certainly has some ground to cover in the consumer market, web servers and many workstation type systems will function fine as Linux systems.
SW,
It despends on what you call non critical. File, Auth, Mail, Print is windows and will be that for a good long while but is your source control server non critical? are your web servers non critical?
As a fellow MCSE might I recommend Red Hats training its far better than the Linux+ stuff..