Hi @edberner ,
With the new Count feature, the first example you are looking for should be fairly simple. If you’re on the Product dimension with Total Mode turned on, you can go to Measures → Count (w/ arrow) → Customer. Then just make sure your Period is set to “past 3 months”. That should show you the count of customers that have purchased each SKU over the past 3 months. Then just using sorting.
I think you can right-click in that Count column and add a “greater than” or “less than” qualifier, but it seems like good old Advanced Search is grayed out when using a Count dimension. Good luck!