I have they are rare though. once ever 10 years for a good sized project seems right. Where they habpen I wouldn't expect anything other than the exact hardware to reproduce them so I'm still not wanting a workstation live the target.
Most optimizer bugs are about the optimizer making assumptions about properties of the source code, not assumptions about properties of the hardware. Certainly it can go both ways, but of course you want to test the actual output of the optimizer. Doing otherwise is not at all what I'd call standard practice.