it depends on the benchmarks, especially in CAD. my 1700+ oc'ed to 2600+ (thanks, shimmishimm!) is BLAZINGLY fast in CAD. i have never seen anything like it. things that used to take 10 seconds happen almost instantaneously now.
gaming is always fun, and from what i've read, the athlon platform is superior to the p4. for me, amd is the way to go, hands down. i'm going to wait for 64-bit computing to go mainstream before i jump ship tho.