We're approaching a point of replacing several of our developer PCs and would like to move up to 64-bit to maximize the hardware/life of the PCs but we also need to support several legacy VB6 applications. That said, Microsoft says it's not supported, but that doesn't necessarily mean it doesn't work. However, support's not important on a dead tool so long as it's functional.
Speaking from experience (I run VB6 almost every day in Windows 7 - 64 bit), there is no problem getting it running, in fact you do not have to run it in any kind of compatability mode. There are a couple of Caveats though: