Strange. I'm currently running 32-bit Edgy on an AMD64 machine - Athlon 64 3000+, socket 754, ABIT NF8 motherboard (NVIDIA nForce3 250 chipset). Every hardware item works just as well as in the 64-bit kernel. And, some programs (Flash, the full Sun Java package, among others) are simply not available for 64-bit.
We've been waiting for applications like those to become available and that's why I'm still on 32-bit OS. I had 64-bit Kanotix, running kernel 2.6.15 compiled from sources from www.kernel.org
before, and on installing Ubuntu I went 32-bit because of that... I decided not to go 64-bit until it "matures" a little.