The most commons causes of slowness I've seen are: 1) Interleaving changes to style and requests for layout information: this causes lots of relayouts instead

The most commons causes of slowness I've seen are: 1) Interleaving changes to style and requests for layout information: this causes lots of relayouts instead of just one. 2) Using libraries that under the hood helpfully end up doing item #1 for you. 3) Using complex graphical effects (blurred shadows are a common one, as are certain gradients) that are actually very expensive to implement and may not be amenable to being GPU-accelerated.