it's awesome. it's my favorite neogeo/arcade game of all time. it allows freeplay...and trust me, you will need that badly. some parts of the game get a little frustrating because you keep dying. it allows you to save your position in the game, i'm not sure about metal slug 6 though
the sprites are awesome. they smoothed out metal slug 2's choppiness. metal slug 6 is an awesome addition, because i think it was only available in the arcade. you get to change weapons and use melee attacks in #6
as for controls, i just stick to using the wiimote on it's side, like an NES controller. i tried the nunchuck control and it's ok except that i keep shooting up or down when moving left or right.
the arcade style with chuck and wiimote is just wierd, i'm not sure who would use that
the tilt wiimote control is ok, but takes some getting used to.
they also have the simpliest control, which is just using the chuck for everything. only problem is that i still occassionally get the same trouble with the chuck +wiimote where i'm looking up and down a lot. i need to push the stick straight. this one is cool, but to continue, you need to press + on the wiimote. i wish you could do everything from the chuck
awesome game