I must say I like the idea of creating games and the games I played so far have been really fun. Not all are that well made, but they still have a uniqueness to them. I also wanna play it for the main campaign which looks interesting. How long though does the idea stay fresh?
I say it's worth it for $20 - the campaign isn't very long, but there is an unlimited amount of content being created for it by regular people. So it'll be worthwile coming back to again and again. I had the most fun playing various short games people have made.