It's a big deal because usually threads about MULTIPLAYER Cave Story are like "GUYS GONA MAKE CAVE STORY MULIPTPLAYEAR BUT NO DEMO OR SCREENSHOTS YET BUT I'M GOIGN TO MAKE IT AND NOT CANCEL IT I SWEAR" And then nothing else.
there have been actual playable demos of other ones.
Probably the least shit was Agora's Legend, but even that went belly-up despite having someone relatively competent behind the wheel.