1) Have many bookmark folders on your Start Page
2) Set a background image for your Start Page (unsure if this is necessary but it makes the problem much more noticeable)
3) Invoke Mission Control
The animation will be slow and jerky as in the second half of this video:
This jerkiness doesn't happen if Orion is being run in fullscreen mode:
And it definitely doesn't happen in Safari.
The Mission Control animation should be smooth no matter regardless of whether Orion is in a window or fullscreen, and regardless of whether you have multiple bookmark folders or not.
Version 0.99.129.1.1-rc (WebKit 621.1.2.111.4)
Sequoia (15)