RemoveGrain is not very useful without its brother Repair, but the version you linked works. Also, what version did you compile? The EEDI2 build works and is consistent, though no longer multithreaded. Will all filters with internal multithreading be incompatible with this version of Avisynth?
Edit: Strange request, but could you build
TelecideHints and
FieldHint as well? They're pretty useful for anyone who uses Yatta, even if Yatta itself isn't 64-bit, and should be completely free of assembly code.
Edit2: Hmm, perhaps I should make a checklist of things that'd be cool in Avs64.
Edit3: VSFilter64 available
here.