Thanks for the very detailed feedback. I agree with almost all of the points you made!
The only thing I have a different opinion of is that "Peggle But..." is an original concept. I've personally rated 2 others already! I guess similar games attract people who've made similar games. Interesting to me that they're both pretty different to mine, and to each other. It turns out there's lots of ways to skin a cat...
If I were to refine the concept (which I'm not really planning on doing) I'd concentrate more on the consistency. Like you said, it's a little bit tricky to work out where the balls are going to be, and quite random where they go. Sometimes this is the point of a level, but not always. The physics don't seem to work the same in each of the various environments - in the editor it does one thing, then in a build it does another, and full-screen is another again. Some people's computers seem to affect it too. It's probably something I've done wrong, but a games jam's strict time limit isn't the right place to dig into that sort of bug. Could chase that sort of thing around for days, especially at the speed Unity compiles these days!
I'd also add a time adjust slider. It would go from very slow to very fast, so you could speed up things like waiting for the next shot in the final level, and slow down to react better in the earlier ones.