At the moment in JIRA, you have to wait for the search controls to load (including custom fields, which seem to take ages) before the search results appear, which isn't necessary.

If the body of JIRA's issue navigator came first in the markup before the criteria on the left, the most important content would render first.

This is probably a large change, but one worth recording. You would replace your current table-based layout with one which uses CSS to position the contents of the page.