The CameraQuest adapter I have seems to hit infinity exactly with all the lenses I've tried... except one, and that turned out to be the lens rather than the adapter.
I also have the new RJ Camera adapter (same one HansenTsang has) but haven't had a chance to check it yet. I received this free from RJ after buying one of his early adapters which didn't quite reach infinity. However, even the early adapter was off only by a few hundredths of a millimeter, so I doubt that floating elements would be affected.
Note that if your imaging chain includes any other adapters (such as LTM-to-M adapters) these also can be a source of deviations. And I suspect that some M-mount lenses may not be 100.000% correct at infinity, but the M-mount rangefinder doesn't show up the difference; it's only when examining the image at high magnification in the G1 finder that the issue becomes apparent. So there are other potential causes of this issue than the G1 adapter...