As a pre-Quantum Tab Groups user, I find that Simple Tab Groups is considerably more stable and has a slightly better UX than the old support. So A+ for that. I still feel like there's some missing "secret sauce" here, but I haven't had the time to really delve into the problem to suss out what that might be.

I do love that tab groups are malleable to the user's concept of organization, not some artificial notion such as grouping by website.