Very few enemies take longer to kill. Most of em are still one hit kills, just maybe more bullets fired or so. Some enemies take a bit longer to kill, if they were meant to be "meat sheilds". Aparently there is only one sub-tank in hard mode. I dont know where it is though. They eliminated the other life extending powerups and such in the game too. I am suspecting that the only sub tank is the one that is realy realy annoying to get. Which is a shame cause I realy realy hated getting that one.
There are a bunch of secrets available in this thing too. For example
Bosses from mmz3 and 4 are avalable in level n (you need the aformentioned carts in the ds slot when you enter the room to battle them)
Omega from mmz3 is a boss (also in level n; past the bitch ass pit o spikes and disapearing blocks)
Omega is also a SPECIAL CHARECTER that you get after beat all 8 secret bosses
get to keep X mode when you beat both charecters on normal and have both save files available. On third play through you get to keep x mode when Giro kicks teh bucket.
So yeah, lots of fan service in this one.

