Total dud imo! They need to reduce the charge bar thingy to 8 from 10 or set a maximum number of rounds. As it is, one playthrough takes way too long. Not to mention the type of opponents who ropes, abuses Magik and Kang, retreats on the last turn etc. The experience is just not enjoyable.
Rewards can be nice I guess, but due to the aforementioned issues I am only playing this mode till I get the mystery variant.