Each ng-repeat will set up a $watch on items. (If you look at the ng-repeat source code, most of it is the watchExpression function of the $watch method). Each time an Angular digest cycle runs, each item in items will be examined by this watch function. (Note that in a digest cycle, this watch function could be called more than once).
Each {{}} sets up a $watch. If something like item.property is inside the {{}}s, it is dirty checked at least once per digest cycle.
If a function is inside {{}}s, then that function is called at least once per digest cycle.
I’m not sure about x | filter, but this fiddle seems to indicated that the filter is called at least once every digest cycle, even if x doesn’t change.