I've had it for a while. If you give your workouts a TSS goal, its nice to have it on the screen. Having NP is super nice for long intervals (20+ minutes) and long group rides. IF I don't use because its implied in other metrics. If you look at a race file you can say "I did 30 minutes at this wattage and then 5 intervals at this wattage and" blah blah blah. Or you could quantify that same data in TSS. Either way.