Tempo Trainers

I have recently started using a Finis Tempo Trainer, and have found it invaluable to help me do fast sets. Are there others out there who have used these? Are there ways to use them in a diagnostic sense? (e.g. if you keep decreasing the time interval between strokes by 10% and find the place where your time stops decreasing by 10%, does this give you any useful information?) I really like how they help me keep up with hard workouts, but wonder if there are other ways in which they can be useful. Anyone out there have experience with these they'd like to share?