Having the ability to know how many items of a multi-select item were chosen would be most beneficial. The use case is a form with a fixed value (e.g., hours) applied to a variable number of items (e.g., laborers) to arrive at a total value.
While a repeatable section could be used as a replacement for the multi-select item, the solution is less than elegant. With the multi-select, the required number of "clicks" on the form to select the variable number of items is the number of items itself. With the repeatable section, the number of "clicks" is 3X the number of items ("+" to add, click to select, "Done" to complete for each item).
A count function on the multi-select item returning the number of selected items would allow calculations like those referenced above.
If the Count aggregation function in a V2 repeatable section could be applied to a Multi-Select question in a repeatable section, that might suffice, as well. However, the current restriction on Count aggregation working only on numeric data types limits its usefulness for this use case.