Downloaded this yesterday, still early into the game and loving it. Played Magma (love the dragon mini boss), Concrete (the vacuum elephants rock, yesss, more mini boss love), Plug (ditto to whoever said that hardhat placed right after the disappearing blocks is evil, ingenious evil though), Galaxy (fave master, love how he turns into a UFO) and Splash Woman (owned me, still haven't beaten her).
I'm impressed at how tight MM 9 is so far and how much attention to detail they've paid to sharpening up the level design and not holding back on challenge (one of the best things about this game is how it will make many casual gamers cry). Seriously, this is the hardest MM game I have ever played and I've been an NES gamer since '88. Anybody who ever claims to get the no damage award darn well better have full video proof is all I can say.
And at first I was feeling constrained with no slide but OTOH it sure forces you to time your jumps better. Anyways, 5/5 stars (so far) and hats off to Inafune and the team. You can really feel the newfound enthusiasm he expressed in interviews while you play the game. If his goal was to surpass MM 2 (visuals aren't always up to par with MM 2 though unfortunately which is my only real gripe) while retaining yet expanding on what made the original games so good, he definitely met it. It really is NES gameplay evolved, I cannot emphasize that enough. Bring on MM 10!