I looked at Groupy the other day (and paid for it), but the killer feature, for me, would be if I could tile apps with the tabbed interface. As an example, check out a project like ConEmu, which provides a terminal emulator with the ability to split the terminal horizontally or vertically. Now imagine that - but for any app. So, not just binding instances of apps together, but viewing them at the same time, on the monster monitors which are the norm these days.

Please consider this for a feature request. Personally, I'd use of almost immediately with cmd.exe, but I can see the possibilities, for instance, binding an editor with a set browser window, or a word document with a set browser window with relevant information, so you can view them side-by-side. It's time to take over the world, man (: