Like GP, I spent a couple of hours in this game.
You can tell that this game get a bigger development length, it has an unbelieveable amount of polish. The graphics, from the backgrounds to the character animations, are fantastic. Even though Mario and Luigi are mute (aside from the voice blurbs here and there), they portray alot of personality.
The gameplay is also very easy to get into, despite a kind of slow start to the game (which is minor, the dialog made up for it). M&L is stricly 2-D (from what I played so far), and Bowser has the old exploration mechanic from the two previous M&L games. Bowser's battles and the M&L play somewhat the same, but what makes this the best battle engine out of all the M&L games is that the timing mechanic was tweeked. With timing, you get either Good, Great or Excellent hits. The better the hit, the higher the damage.
More impressions to come as I play through more of the game.