I had Cyrix 486 chips, and those pretty much ruled. I see someone mentioned the Cyrix SLC chips as a negative, and in fairness, they were ultra-low power draw CPUs that were really meant for portables.
They were about 10-20% slower than their Intel counterparts at the same clock speed. I had a Cyrix 80MHz 486 chip that was slower than an Intel 486 DX2 66MHz CPU in most tests.
Plus, there was software out there that simply wouldn't run on non-Intel CPUs.