Views default cache plugin checks $_GET items when building cache item id. It checks for several key in $_GET: exposed_info, page, sort and order
I have some views, where I use exposed sorts, filters and items_per_page. Items which I get in $_GET array are different from those beeing checked by views (sort_by, sort_order, items_per_page, date_filter in my case). Since Views ignores them I run into problems, since I get the same output for every exposed filters value.
I propose to change this I bit. I suggest that we check every value in $_GET, except q. Attached patch shows my idea.