True, but if you could do day to day testing without a VM, even running automated tests against it, that would be a huge timesaver. Then you fire up the VM once

True, but if you could do day to day testing without a VM, even running automated tests against it, that would be a huge timesaver. Then you fire up the VM once a week (or some reasonable interval) to confirm it's 100%. There are platform specific bugs, but most issues I see now with Chrome or Firefox are specific to the browser, not the platform.