As far as I know eValid is a testing tool
developed solely for Web App testing purposes; it uses an approach that differs from the usual approaches in the following
way: A Test Enabled Web Browser has been developed that has a built in feature called Adaptive Playback; it synchronizes automatically even when the generated response page differs significantly from
the one where the script was recorded.
This approach sounds very interesting to me since I'm only doing research in the area of Web App Testing. One drawback of this method
could be that one misses problems that occur
only when using real-life browsers (Navigator, IE).
Since I only know this theoretical stuff described above I would also be very interested to hear about real-life experiences that people have had using eValid for testing Web Apps.