I just beat the fourth boss. The music, control, art, and level design are all fantastic and addictive. I haven't had a chance to play with 3 or 4 players yet, but this is shaping up to be one of the best NES games I've ever played.
I recommend reading the manual, too. It's hilarious.
For the steam version, assigning movement to my Xbox x360 controller's analog stick makes my mage go a little haywire, mainly failing to stop moving when you release the stick. Arcade controls through my ipac work perfectly, of course.
When you guys get your physical copies, I hope one of you shares a picture of the back of the box. I'm curious as to what they did with that.
Save states work on the Everdrive N8, as expected.