I've used servers at work for some years now, but never for anything other than work (oddly enough!).
I recently splashed out on one of the Dell Poweredge 1800 servers in their special offer (dual 2.8GHz 1Mb L2 cache Xeons, 512Mb (2x256mb dual channel) DDR2, onboard SATA, IDE and SCSI, gigabit lan etc..).
It arrived today and I am very, very impressed with it. The case is an excellent design, with great layout inside both for working on (removable ducting for the fans, removable HDD cage, thumbscrews to open it up) and for cooling. The dual Xeons both have huge passive coolers with heatpipes and the cooling is done by a 120mm Delta at the rear and a 92mm Delta up front.
When I first powered it up, I was expecting it to be very, very loud but it is actually quieter than my existing desktop as both fans are temperature controlled (i assume this is the case as there is an initial hoover-type noise when powered on and then the fans throttle down to a quiet hum).
Anyway, I have just tested out Football Manager 2005.
Previously, on my 3GHz P4 with 1Gb XMS3500 and a Raptor, FM2005 took quite a little while between clicks while it was processing (although nowhere near as long as CM4!!). On the server, I haven't had to wait any more than 5 seconds between mouse clicks!
Well impressed!
EDIT - I have just completed a side-by-side comparison on DVD Shrink, encoding an identical DVD on both PCs.
The full time for analysis and encoding on my desktop was 38 minutes, the full time on the server was 21 minutes! Sweeeeet...