why? isn't bitcoin something that could really benefit from the jump to 64-bit?
In short, no. The only benefit to 64-bit userspace is large virtual machines (over 2-4 GB RAM) and applications where a small boost in performance matters more than memory usage (64-bit uses ~twice as much memory). Also, no Bitcoin developers actually use Windows, and I don't think Ubuntu supports targeting Win64.mingw64 should work fine on Ubuntu, but whether the Bitcoin client/daemon actually build for 64-bit Windows is another matter... and as you've already explained, a 64-bit Windows build is fairly pointless at this time, and it'd remain pointless until Microsoft drops 32-bit support (maybe in 10 years
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