Since this thread is silent again, I decided to bump this by informing you about a new challenge system.
It was tried out today for the first time ever and even I got to win one:
PIC
So basically, Banchobot tells everyone the challenge in #osu and the fastest one to complete it is the winner. For example, that one I won was a "Ghost Buster!" challenge and in that challenge you'll have to pass the map mentioned with Hidden mode.
Of course, I used double time + hidden becouse that was faster.