I have a couple hymnal apps in the Play Store built with Kivy, and reviews suggest that performance is a problem for some people, especially scrolling through long views. I'm in the process of rewriting them using HTML and JavaScript in a WebView.
That being said, Kivy is really nice to work with; the documentation is good and it's a well thought-out library. I'd enjoy using it for future apps that don't happen to have long views to scroll through.
Did you use ListView, or did you roll your own ScrollView managed content? We are sorry about the state of ListView currently, and plan to redesign it soon, it's really not optimal currently, and not offering a very useful interface either, so maybe you could fix you issues just putting a GridLayout in a ScrollView and fill it as needed (i documented a way to do a publisher/consumer using threads on my blog, it's efficient for these kind of things).
Initially I used the ListView, but found performance problems on every device. I then rolled my own using a layout in a ScrollView, and it's better, but still troublesome. I'll compare what I've done to what you wrote about and see if I can improve matters.
That being said, Kivy is really nice to work with; the documentation is good and it's a well thought-out library. I'd enjoy using it for future apps that don't happen to have long views to scroll through.