In defence of Parallels here, the issue with the things appearing huge on external monitors is down to windows more than anything. It's not Microsoft's fault either though, it's not common to have two monitors with such different pixel density.
Windows doesn't allow for different DPI scaling on a per monitor basis. I've not bought a Thunderbolt to VGA yet so can't try multiple displays, but the fix that downscales on external monitors sounds like something that isn't necessarily easy to implement.
Unfortunately it does sound like it's not working that well for some people, but i'm eager to try it myself. The Retina issues are mostly new problems that won't have been encountered before, so i'll accept they will take time to iron out.
Just so long as they are fixed in PD8 and we don't have to wait for PD9 of course ;-) If the downscaling on external monitors doesn't work well i'll just resort to using two external monitors with "normal" pixel density for Windows when I can so it won't need scaling at all.
Would be interesting to see a photo of somebody stretching a window between the retina and an external monitor to see how the downscaling is handled when something is across two screens.
I've not tried any other Mac virtualisation software, but I would imagine other vendors have the same issues in these areas.
Has anybody got the fixed built and tried the downscaling on external monitors? Does it work well in the slightest?