stick with linux. my ESX servers at work have been up for the last 6 months, not a min of downtime.
also, MS clustering requires Active Directory. cluster configuration is not only held on the nodes, but needs AD to function and info is also stored there. it is mostly meant for business structures. the main thing to look for is an application that is "cluster aware" like sql, exchange, etc.
if you have the resources, take a look at polyserver. it is horrible software, hated supporting it but allowed multiple servers to connect into the same storage(has to be fiber channel though).
you could have your 3 machines doing the same thing and place them behind an application level load balancer.