Comment 6 for bug 1384374

After having another look at this we'll need more time to investigate and find the right balance and a solution.

What you can see currently, the worse experience is happening when you swipe between scopes for the first time after the dash is loaded. This is because when you swiped from scope #1 to scope #2, scope #3 is queried and its contents created, which is a heavy enough operation to cause brief (or less brief) UI thread blocks resulting in the stutter.
After all scopes are loaded, however, you can see that swiping between them is smooth, even though they do grow the number of items to prepare for the user swiping down in that scope.

We need to spend the time to understand where the blocking comes from and reduce as close to 0 as possible, and if that's not possible, potentially employ a few workaround fixes by the use of timers to defer delegate creation or similar.

FWIW, this isn't as obvious on vivid as it is on RTM simply due to the number of available / installed scopes.