One thing that did seem to slow down my device a lot was Modest (the mail app). I had 5500 messages in my inbox, so I am assuming it might have affected performance a lot while periodically polling the account. I trimmed it down to 700 mails in the inbox and at least it *feels* a lot snappier now. Running newest firmware (42.11).

I decided to test the game right now with the trimmed down mailbox. I closed down all apps, so that my dashboard was empty. Bounce ran lag free on the waterfall level except for the very beginning, when the camera moves up the brown slope, before the actual game begins. The most common stuttering place, the waterfall before the logs fall down, ran absolutely silky smooth. It stuttered like crazy before, when I watched my wife play the game.

So, sorry. It appears I was incorrect about the lagginess of Bounce.