*THIS POST CONTAINS SPOILERS*
All right, I finished this on Hyper mode difficulty just recently, and I can safely say that this is the hardest Metroid game just to play through normally when you factor the hardest difficulty levels. The bosses are very difficult and tedious this time around, and you'll find yourself going into hyper mode quite a bit even against normal enemies. Good luck beating Pirate Commandoes and even Metroid Hatchers efficiently without going into hyper mode or using the X-Ray + Nova beam trick.
And don't even get me started on Phaaze and Dark Samus. Hyper mode Dark Samus is by far, the hardest boss in any Metroid game, period. Not only do you have to just beat DS, you must beat her with enough energy remaining so you don't die instantly against the Aurora unit. To be honest, that was not a problem in Normal and Veteran. Good luck to anyone about to fight Hyper mode DS. Trust me, you'll need it.