Don't get me wrong, I really like the Illinois Death Certificate Index and am very appreciative of it.
However, if I could only make one change, it would be to add a new search option:
"every county except Cook"
With the exception of my grandmother-in-law, all my Illinois families (and there are a lot of them) are well outside of Cook County. When I perform a statewide search (which is often necessary), I really only want the western third of the state. The results from Cook County overwhelm my results.
Of course, I can import the results into a spreadsheet and sort them by county and delete the ones from Cook, but it would be nice to have a "everything but Cook" search option. And Illinois is not the only state whose population is dominated by one metropolitan area.