I have been using the free version of this for two years of teaching fitness classes and decided to upgrade. For my uses it has been the best timer, changing the times as needed for circuit, HIIT, Tabata whatever and it is great. I would give it 5 stars, as it really is worth it but find it difficult to change the timer sounds and store listings of my set ups so I dont need to change them prior to every class. Early on, before an upgrade on the free version I had a listing hence buying the app, but dont know how still, I say, stick with the free version.
Sabara88 about Interval Timer Pro, v3.0.2