I love that you have the option to work on solo challenges and also to compete with other developers. Creating AI's that compete playing a game against another AI's is a great experience. You are not evaluated by your specific knowledge of some specific subject, but by your ability to solve a problem with the tools available. And time is not a factor most of the time; most contests last 10 days, so you have plenty of time to think and improve your code.

You can improve our skills, explore type of algorithm that may not be your core day to day work, or simply learn new languages by comparing how you would do in your favorite one and the new one. There is a lot of way for you to enjoy the platform. You can even just do dirty code to quickly resolve as mush as puzzles as you can if your more interested in badges and gamification, than code quality. It's up to you to found the fun that match your profile.

It is fun, you can use the language you want, the competitiveness is well done and simple, the community is really nice and helpful.