I'm glad the show ended. It's better to not let things die pitifully after 12 seasons or so like The Fairly OddParents or Spongebob.
But to be honest, I never really watched Regular Show until I saw the first season this past summer. I only saw a few episodes back when it first came out when I was 9 or 10, plus, it didn't air in Canada until I stopped watching cartoons on TV all the time, so I never really grew up with the "new generation" of CN like Gumball and Adventure Time.
Sucks that it ended though, the episodes I saw were quite fun and entertaining to watch.