I spent a long time in Marvel Heroes on Monday. Typically Monday is the best day to power level your characters. I brought Thor from 55 to 60, Moon Knight from 47 to 50, Hawkeye from 30 to 50, and Captain America from 30 to 45.
Monday is Midtown Madness day. The bosses that normally occur have added loot in the form of chests full of loot and experience orbs and fortune cards that could turn into one of all sorts of items. Combine this with the added experience bonus for Avengers and you can really make some progress is just a couple hours.
As it stands, I have the following characters unlocked:
Cable at level 60
Captain America at level 36 on his 2nd prestige run (meaning I got to 60 twice already on him)
Cyclops at level 60
Emma Frost 9
Invisibile Woman 37
Jean Grey 60
Moon Knight 50
Ms. Marvel 60
That’s a total of 17 characters I can get to 60 and doesn’t count the characters I can play to level 10.
Maybe I play a bit too much…