After about 2 weeks of using Groupy I love it. It seems like it is part of Windows.
That said - it is extremely irritating when you have a lot of windows open to navigate through the "hot drop" window targets when moving a window. I am dragging windows in and out of groups all the time as they are inadvertently combined. I assumed I would get used to this but 2 weeks and I still do it...
How about simply making a timed delay before the drop target "insert into group" appears? That momentary pause shows the user is clearly trying to group. I tried using the existing "if CTRL is pressed", but I find myself forgetting that groupy is there when working.