I demoed gymatic long ago when it was named something else; I wanted the automatic rep counter feature; but it never really worked. So that may have improved over the past 2 years. I used Gymaholic for tracking weigh lifting though a lot. I demoed lots of other apps and I did think gymaholic was the best overall. It is useful if you have set workouts you repeat and you want to use your watch to time the rest, and you want to keep a log of your workout day to day. Completing sets and and exercise using the watch is pretty good. There are lots of other features on Gymaholic that I never used, and in the end, I don't really need that much tracking so I have gone away from using. But I like the rest timing, so may still use it.
For automated rep counting I have an app Fit counter. that feature is the only thing it does. It does work, sort of or some of the time, so I would not say it is a super reliable. I am using it just for tracking kettlebell movements, which should be really distinctive, but it seems very sensitive to when you start the first rep. So if you time the first rep perfectly, it will count accurately, if you miss the countdown and start early or later, it gets confused and will count randomly or not at all.