A little Firefox extension called "eBay Negs" will allow you to open up a window or tab that shows an eBay user's negative and neutral feedback only. No more wading through hundreds of feedbacks to find the negs . There's also a version for Internet Explorer.
For Firefox: http://www.toolhaus.org/negs-firefox.html
For IE: http://www.toolhaus.org/negs-menu-IE.html
I haven't tried the IE one, so I can't vouch for how well it works, but the FF version works beautifully. Just be sure to follow the installation instructions exactly as shown, and don't try to install the version from the Firefox website if you have version 1.5 - the install will fail.
When using it, make sure you right-click on the user's NAME, not their feedback score.