I was initially annoyed by Alt+` to switch windows within a program group but now I find it useful
Oh, you're joking. They will have pinched that one from Apple. I've gotten used to it as well, but it's one of Mac's worst features, and completely opposed to the notion of activities over apps, which I remember was a big thing for Gnome when they were discussing their v3 vision (which at the time I found compelling and is probably best realised today on Windows Mobile).
Personally, I left Gnome because it felt unrefined and designed for a device other than a conventional laptop (i.e. one without a touch screen). I left KDE many years before then because I found the UI too busy, but they seem to have left that behind them so it might be time for me to take another look as well.