The demo contains four of ten playable characters, three stages to try, and playable in either single player or multiplayer. And given the intense action some of the previous trailers have shown, multiplayer might be a necessity!
Sadly I have not been able to try the demo yet myself, but I've gotten solid impressions from friends, especially concerning the game's mechanics and original music. Only complaints have been toward the abrupt screen transitions, which are set to be fixed as it is.
Be sure to give it a shot; I think multiplayer has long been overdue in Mega Man action platformers. If Capcom won't make it, the fans will!
Thanks for the tip, Knozz!