I would love a way to perform incremental searches in both Toolbar and Explorer.
Toolbar's IS would somehow integrated into the existing search box and would essentially hit Enter for me after every character I type (after a minimum of 3 characters or so have been entered), which would allow me to stop typing as soon as the search results seemed narrow enough.
Explorer's IS would be activated by a keyboard shortcut (my favorite is Ctrl+I); would not bring up a dialog box (the status bar could be used to display what characters have been entered into the IS so far); would start working with the first character I type; would scroll my snippet to the next matching result; and, upon my cancelling the IS by pushing ESC, would return my cursor and scroll positions to where they were when I started the IS. This is essentially exactly how UltraEdit's IS works. I am a huge fan.
http://en.wikipedia.org/wiki/Incremental_find