> Of course no-one wants to have to support every distribution out there,
> but when the "regime" is happy to indulge Windows users with the latest
> and greatest, but they won't even entertain a second choice of
> well-regarded Linux distribution
But these are not the same. In many ways the difference between RHEL-5 and RHEL-6 will be significantly less than the difference between RHEL-6 and Ubuntu-10.4, even though they'll be released within months of each other (as against years).
Also any support problem that hits both will require at least double the work of using a single vendor.