I'd be up to try it--what's it like?
I've unlocked everything in Kingdom Rush, I still play it but alas there's no leaderboards.
KR is next on my iPad list. I feel the same way as you about PvZ, unlocked everything but just playing for fun. No way to advance on the leaderboards with numerous fake scores populating the top and the rest of placement dependent solely upon grinding.
Run Roo Run is a very simple game so there's no inherent "challenge" to finish it, but rather an addiction that arises out of trying to better one's score with subtle accuracy. It's a single screen platformer, with only one action - touch to jump. Simple and easy to play if you're nursing a child (latter doesn't apply to me). However, the real rush is in finding the most effective and timely jumps to get your finishing time lower.
Same kind of addiction that Doodle Jump or Fruit Ninja seem to provide, except without the annoyance of infinite levels or the constant 3-star judging of Angry Birds.
Sorry B, no Android, iOS only.