I'd like to share some experience we had with uploading ATF images (ETC2) to the GPU.
Our code used to upload ATF files one by one: when one upload completed, the next upload started.
In order to boost application loading, we allowed 2 consecutives calls to
uploadAtfData on the same frame.
While loading times imporved by not-too-much, crash rates went up by 0.7% (!).
We did not test this issue on iOS.
If anyone experienced similiar issues, feel free to share.