I onced worked for an Organisation that used Winrunner and LoadRunner by Mercurary interactive.
They had bought a very large peice of software from a third party who had a habit of creating more bugs than they fixed.
They wanted a tool that they could record tests into and then replay overnight to check that a new version did not break anything that previously worked. They had some success, but it took along time to set the tests up and sometimes the scripts to test would fail as the mechanism of the screen had changed although the functionality was the same. Winrunner did not alaways cope well with this.
However, this was about 3 years ago, and things move quickly so I'd say its definatly worth getting an eval copy and taking a look.