Tried running the same download experiment today with FF, and virtualization seemed to work fine. Download was visible in FF, but did not appear when I switched to Explorer unless I told Avast! not to virtualize downloads. Back to Opera to see if there was something else going on previously or if this is an Opera issue.
UPDATE Download still comes out of the sandbox with Opera no matter what the download virtualization settings are. ???
UPDATE2 Chrome seems to work OK
Will keep running them to see if anything else appears of interest.