ESET NOD32, hands down, no contest.
I use only NOD32 and have it's Vista 64-bit version working great on Windows RC-1. It detected and removed viruses just fine when I was scanning a co-worker's drive via USB to remove viruses for them (I do PC work on the side apart from my full time job as a software engineer).
The "detection in the wild" and scanning throughput of NOD32 beats all others, no exceptions. It also has the smallest footprint of any of the big name Anti-virus packages out there.