As someone who has tried several gym apps, this one has been my favorite. Clean functionality, good rest timer, and good built-in data base of exercises.
Small areas of complaint are that the cardio exercises are not set up to track all the metrics that Im interested in (time, heart rate, calls) and there is no interval timer for speed based cardio work or superset type lifts.
Jimmy7310 about Gym Genius - Workout Tracker: Log Your Fitness, Exercise & Bodybuilding Routines