For me it's the winning.
The most rewarding aspect of playing at Chess.com

Interesting. To me the most rewarding aspect of playing at Chess.com is not winning or losing but all the 13 year old kids that decide to write me hatemails because I beat them at bullet and didn't want to rematch.
Huh - you find hate mail from children rewarding. Have you held on to a couple of the more particularly vicious examples to perk you up when you're having a bad day?
"I had a bad day at work and my boss yelled at me, but at least I know that little Timmy from Akron thinks I'm a rotten piece of !@#@ and hopes I die of cancer - and no one can take that away from me!"
I enjoy the opportunity to get competitive games as there are so many people at or around my skill level on chess.com - it's hard to get that in person, at least where I am.

For me, the most rewarding aspect of playing at Chess.com is my group of friends, NICU_57 & HIS BEST FRIENDS. I'm proud to have a lot of friends here
I've met a lot of great people and avoided some of those anonymous nasty interactions by not playing live chess. More committed members show up in the tournaments and team matches. I also agree that the opportunity to play so many different opponents of similar levels is a huge benefit of the site. Thanks for the good feeling post.
To me the most rewarding aspect of playing at Chess.com is not winning or losing but all the fine people I meet from all over the world.