I hate Dell desktops, although I do like their monitors. Dell desktops tend to over-optimize on power supplies and other components, such that you can never really upgrade them later.
+1 for supermicro and they're fun to build as well as bomb proof
Dell's done some dumb stuff, and the newer gen models are a nightmare to figure out (limiting number of disks for no reason, requiring 2.5" on some models but not others). Plus they gouge you to get a functional KVM ($300+?) But they've been far more reliable than Supermicro, in my limited experience.
> Intel developer machines
Several of their new technology server motherboards were actually OEMed by Supermicro -- stuff like the boards for testing TXT, etc. Intel is actually getting out of the motherboard industry entirely. I think Supermicro was mainly involved in the server boards, not their desktop boards -- bigger manufacturers usually used intel reference designs but still made their own board, so I think it was a low volume business.