Wow! This is a quality developed app. Completely worth the price.

Clean, simple, beautiful UI and easy to use. Does what you expect it to do. Audible countdowns and rests are great.
Watch version doesnt seem to stay alive and theres a bit of lag. Personally, Id say thats a Watch OS issue.
Only bug Ive found is if you end a workout early and return to start it again the next time, it might need you to close the app and open again. The start could be off.
However, amazing App. Well worth the price and you wont be disappointed. Such a nice UI and great tool. 4.5 stars.

bmeraly about Intervals Pro - HIIT Timer, v2.0