I've had some good tests with heavy sprite usage, constant text updates and a few physics running at the same time on the following;
Samsung Galaxy S (Originally Android OS 2.1, updated to Android OS 2.3.5)
Samsung Galaxy Y (Android OS 2.3.5)
Sony Erickson X8 (Originally Android OS 1.6, updated to Android OS 2.1. Now running custom kernels and roms at Android OS 2.3.)
No slow down on the Galaxy S, slight slow down on the Y and the X8 struggled initially during the load of assets but picked it self back up again before struggling with physics objects.
I've got a Tab, Note, Kindle Fire, HTC Sensation and Sony Ericsson Xperia Arc to test on come Wednesday (Benefits of working at Mobile Phone store

) so I'll post some hard figures and try and get some screen captures too.