I think, if the slider of overlay layer move down, it was more usefull and easy to use.
Now, if I want to see a map on overway layer, I must to look under my hand. I can't to move modal window.
I've attached a file with screenshot.
İndispensable when overlaying satellite maps, comparing different maps for missing data, or anything layer wise, really.
Now to change the opacity one has to open the Overlay dialog and guess the transparency over dimmed screen. Not very convenient, let alone quick.