Y2K remediation, sample size about 50 people. Corporate IT charged 2 hours for PCs, 1 hour (min charge time) for Macs. Most PCs took at least 2 hours, the worst case was the guy who was down for 3 days. Most Macs took less than 30 minutes if Corporate IT did the updates. But most Mac users did this themselves (in part saying, "I don't trust corporate to mess with my Mac.") Most of the required Mac patches were for Microsoft Office, Adobe Acrobat and other 3rd party products. The required change to Mac OS X was to set date display to 4 digits.
Where I used to work, the Macs were mostly self-supporting. When someone needed help, s/he would send a message to the internal Mac user group, and usually get a good/authoritative answer. The few times we needed to work with corporate IT involved hardware problems.
Laptop 'survivability,' sample size about 40 people. I was on a project with about 75% travel for several years. No one had a machine that lasted 3 years without a repair, most Windows machines were replaced within 2 years (ThinkPads lasted substantially longer than the Dells, HPs and Toshibas that most people had.) My first Mac lasted almost 3 years, it had a motherboard failure at 34 months. I dropped it off at the Newport Beach CA Apple Store late Thursday night, and got it back at the McLean VA Apple Store Tuesday AM. My second MacBook Pro lasted 5 years, but for the latter part of that period we were on less travel. I did have that machine knocked over and the screen cracked, but that's not an Apple problem. I handed that machine in when I left the company, it still worked and was usuable but a bit slow. One of the (removable) batteries had failed, the second was weak (and I had a 3rd replacement battery), but the hardware was otherwise fine.
As usual, Your Mileage May Vary.