I like groupy and the possibility to group windows and have tabs, it is great.
Also that i can group different windows not just the explorer.
Several years before (win 7) I used qttabbar (original one).
As it is discontinued I searched for new software and came to groupy.
There are still some features that I miss from qttabbar, like double click do move folder up, favourites, preview and so on.
I think you are aware of qttabbar, nevertheless i wanted to mention it, so maybe some of its features could be integrated in groupy.
There was also a different branch of qttbarbar by Quizo who had more new features (but sometimes a little bit unstable).
Haven't used this one for win 7 but the old one from the link (think 1.5 beta 2).
I like groupy, especially it works like a charm for me.