I used the free version at the beginning. It was good as a tracking device of how many miles I was putting down and to check the routes. As I started training with HR and power I opted for the premium version. I like it since I get to check detailed info about my rides as well as how a stack up against people around me. If you are at least a bit serious about riding the 6mo. is worth it. Other sites that are much more detailed but also much more expensive. At the moment Strava Premium does it for me.