I picked this up tonight, and overall I'm happy with it, but not as happy as I ought to be. I was really hoping they wouldn't blight this port with the same problem SMB2 had: Annoying, pointless voice. There should really be an option to turn the voice off and have it sound like the original game, because hearing Mario saying the same 3 things over and over again gets VERY old very quick. Also, when you talk to the Mushroom Retainers in the castles before going to the Airship levels, they added the world's most annoying sound effect: "text chatter". Why they chose to do this is beyond me.
Graphically, it's pretty perfect. Aside from altering the menu a bit and moving most of the information to the top of the screen rather than the "status bar" format the original and the SNES port had, it looks exactly like the SNES version in the stages. They took out the larger portraits of the characters that were in the Match Game houses originally, but that's not really a big deal.
The important thing is that the gameplay is still intact, and aside from the annoying voice (and the music's slightly degraded quality), it's the game I remember from my childhood. The one alteration to this is that Luigi is not merely a clone of Mario, but rather has his taller look and hover-jump from SMB2, which is a welcome change (even in 1988 I thought they should have kept him like he was in SMB2).
I don't have an E-Reader, so I can't comment on the new levels, but my friend has one, so I'll be able to try them out soon enough.
So, finally, the best Mario game ever is finally portable, and aside from the aural annoyances, it's great. Go buy it, especially now while it's still early ; )