I was thinking for a while about some other user suggestion regarding 'fps' , and maybe it would be possible to built-in some kind of benchmark tool to Sencha Animator in distant, future versions? It would show fps and some kind of units, 'points' like in cpu/gpu benchmarks. Than you could compare amount of cpu power that is required to playback this animation on i.e. iPhone 3GS, iPhone 4, iPad or HTC Nexus..
This tool could show cpu/gpu drain on a graph, so you can track critical moments in animation, when i.e. animation wouldn't run fluently on some older models of phones. This would play nicely with some "debug" tools suggested by other user (tool for checking multi-browser compatibility).

Cheers