ECC is good to have if you do financial or scientific work with your PC and want to be as sure as possible of the most accurate results. Or if you are running software RAID-0 (most PATA and SATA integrated controllers and inexpensive add-on controllers). Most AMD based mobos don't actually support ECC anyway even if it is supported in the chipset (as it is in most Via chipsets - ECC is not supported at all in other brands of chipsets except maybe in 64-bit - you have to pry the info out of the mfrs for some reason the spec sheets aren't up-front about it) . Some Intel chipsets/mobos do support it, some don't. Server and workstation mobos almost always support ECC. ECC RAM is not THAT much slower.
.bh.