This is one of the items that is tested in your Windows 8 App when you use the WACK.

If you are in Southern California, please email this post for more information on getting a token for your app by June 30, 2012!

 

Animation Performance:

Sustains 60 frames per second

Fast and fluid applications should redraw the screen at 60 frames per second.
Drawing with high frame rates is most commonly achieved by leveraging the GPU to do the drawing of the scene. You can accomplish this by:

Using the Windows Animation Library (if writing app with HTML/Javascript)
Using the native animations in XAML
Leveraging independent animations as much as possible
Independent animations are animations running off the UI thread (most often in a separate hardware accelerated I thread

References:
Animating your UI in Metro style apps built using HTML & Javascript
Standout with styling animation in your XAML app

Reference (HTML)

Animating your UI in Metro style apps built with HTML and JavaScript

Reference (XAML)

Standout with styling animation in your XAML app

Other References

Performance tips for animating Metro style apps built using HTML & JavaScript