I like the concept. I use Strava a lot for cycling, but it's not very good for non-cardio activities. Lots of people I follow also track their strength workouts on Strava, but I haven't done it myself as I find it hard to track progress when the system is not made for it.

Before I have used Fitocracy, I'd say this may be the biggest competitor to this, as it is (at least 5 years ago when I used it) more tailored for strength, where one can log specific exercises and track them over time.