Yesterday, today and tomorrow, I'm in Londinium working with a small to medium business. Under a hundred Lotus Notes users, but all remote to the office, and with huge security and reliability requirements. Its not quite "life and death" information, but I suspect the users of this application would think otherwise..
Interestingly a large number of servers, all of which are already on Red Hat Enterprise 3 (and being upgraded) or are being rebuilt onto Red Hat Enterprise 4. Very cool indeed. In fact, the only serevr that WONT go onto Linux will be the BlackBerry Enterprise Server -which at the moment HAS to be on Windows. It would be interesting to see the BES server move onto multi-platform support in the future, but this would require massive reprogramming - currently it uses the freeware version of MS SQL as a datastore.
Does BES being on Windows present an issue to you ? Would you categorise "Windows" as a primarily supported OS in your datacenter, or as a legacy supported OS ?