Because we only have one win64 builder machine in production, and all tests were failing, we'd just done one win64 build per day. Now that win64 tests are passing, it is worth doing win64 builds more often... as much as the one (soon two) machines can keep up. Maybe we can do this using queue-collapsing just for win64? The win64 machines will not be able to produce builds for every checkin until we get the refimage work finished (bug#565402) and the next batch of ix machines installed into the new colo. However, this change should help win64 developers in the meanwhile.
I don't think we should be doing anything further that makes 64-bit Windows builds appear fully supported until we've got a build pool. We're not shipping this platform for Firefox 4, so waiting even a month or two appears to have little downside. Also note that one of the two machines will need to be offline for an extended period of time while the ref image is finalized and pulled from it, which cuts our already limited capacity in half.
After thinking about this a little bit. We have no developers working on anything related to Windows 64 since they should be focusing on blockers for FF4 and as we know Windows 64-bit will come shortly after we ship. The plan is to have a ref image by Sep 17th (before work week). We should not waste time on this since in few weeks we will have the real thing.