A good game, but nothing amazing.
Super Mario 3DS Land brings to the series a 3D feel in a classic Mario environment. You'll encounter several old-school items and monsters, as well as a few new things. In a nutshell, Super Mario 3DS Land is worth the play through if you're a Mario fan, but it might leave you disappointed.
I bought the game today, on release, and I am almost 100% through the game. That being said, it's very short, and very easy. I currently about half-way through the additional levels that are unlocked when you beat the game and I'm sitting at 152 extra lives. That doesn't mean that it isn't fun, but in terms of content, it is somewhat disappointing.
The only other thing I will add is that the controls feel a little clunky, at times. I find that Mario's jumping speed in this game has been reduced substantially and it takes some getting used-to when you're having to make quick-reaction jumps in a 3D environment.
I rated the game at an 8.0 because it does feel and play like a Mario game. It could have been harder (especially since they added a free-ticket to any level you die more than 10 times on), but otherwise it was a fun play.