The specs outlined by the military make the slowest outfits cost way more than comparable civilian ones. I used to work for a military contractor who made ruggedized computers as one business line. I needed a rugged field computer for my own work with a civilian client....I got a slow rig that was very pricey, because not only was it protected against rain and mud, but also Electromagnetic Pulse and shrapnel, and was able to plug into tanks from various countries, etc.
I am using a Dell desktop, not ruggedized, not anything, computer in my job. The OS is XP pro sp2 . Most of the people in the squadron use laptops (again, not ruggedized) with a docking station. There is some kind of special software that allows them to send alerts (lightening nearby, etc.). For email we are using Outlook with some special features that delete certain attachments.