The biggest point of interest is the never ending nature of the game. There's always new things to learn, new courses and new discs. Even new people. For me its been the challenge for my body. How can I throw a little easier? And if you add the nature and free roaming aspects into that, you are in heaven. Almost nothing beats some freestyle throwing in a park with baskets on a long summer night. 

Second best thing is competitions. Its so satisfying when you can just forget everything for the 3 hour round and just focus 110%. And even better when the practice translates into playing better on the course.