The enjoyment is obvious. I will just try to tell you examples of how I know that, so you can get the flavor.
At first, I did math enrichment for select students (who could afford to miss the regular math lesson). One of my threatened punishments was that if they did not behave, I would send them back the class. That always worked (for a while). I do not think my math enrichment is more enjoyable than video games or playing with friends. But it is much more enjoyable than the normal math class.
I am greeted quite enthusiastically by one class. Once I was at a gas station and they were at a nearby stoplight, on their way to a field trip. I had the pleasant embarassment of having to say hi to a class of sixth-graders waving excitedly to me from a bus.
I can tell one student likes me because he is always smiling, always seems excited, and a teacher told me how he talks about my math enrichment. Another student seemed like she didn't like math enrichment, but I heard from her mother that she does (and she talks about it).
Even most of my failures are successes. The girl I voted least likely to be enjoying math enrichment did not smile for the first 4 sessions. But I got a smile of success from her on the fifth session, and since them I have gotten them occasionally.
Another student was a failure -- he did not enjoy math enrichment and I suspect he wasn't learning anything. Then he had a few successes. I learned to try to get the problems down to his level. I discovered that he could learn at a normal rate, he was just starting out behind everyone. He in turn became very comfortable with admitting when he was lost. Now he succeeds often and usually functions at the level of the rest of the class.
One day, a third-grader was out from gym. I asked if he wanted to do math enrichment. He didn't. His teacher encouraged him. We started. By the end of the 40 minutes, we were having a grand time.
I had one student who was very poor in math. By the time I realized that, most of a year had gone by. I would not say I taught him much. But in his words, I "taught him that math could be enjoyable."
My five-year-old woke up one night and couldn't get back to sleep. She came to me. I said, "Do you want to do math enrichment?" "Sure," she said happily. And so we did math enrichment.