The new custom features are exciting and keeps you coming back for more, but the unfortantly there are some letdowns....
I quite enjoyed the 3D in the game, it made the game seem more vibrant but it may take a bit of getting use to, as if you played the previous Mario Kart on the DS or the Wii, but after a while you'll start enjoying the vibrant colours, or the gloom of the caves or makes it feel more realistic.
The music seemed suited, personally I didn't really take up to the first track's music and it seemed a bit repetetive, but nevertheless fitted in. I quite enjoyed the remixs for the retro tracks, as they keep to the tune but expands on it and makes it seem more like that your there (Mainly on the jungle levels). Overall I enjoyed listening to the music.
The hang glider provided a new strategy, is it better to speed down below ground and try and reap hidden benefits? Or is it worth staying in the air and collecting coins? Even though it main seem important in some stages, one of the big difference and the problem that will drive you insane are coins.
In levels you can collect coin which boost your karts speed (You can collect a maximum of 10) therefore making you faster, but if you get hit by an enemy or projectile or fall off a cliff you'll lose 3 coins. This changes the whole game. Is it worth going a bit off track to grab a few more coins, or are you better off going on course?
The only major letdown was that there was the removal of Missions (In the previous Mario Kart DS) which was something to play and challenge yourself. Also there isn't as much customization for just playing in SinglePlayer. You can only either do Grand Prix, Time Trails, Balloon Battles and the Coin Collector. There is no option to change your name, look at your records or just play a course on custom settings.
For me that was a letdown, but the thing that pulls that game from the pits is the coins, the customization and the remixed music and the amazing courses chosen and made. The new characters were a great addition (I felt there could've been more) and I enjoyed the game overall.
I highly recommend it if you just bought a Nintendo 3DS and have played the old Mario Karts, you'll enjoy the new characters, playing as your Mii and customizing your kart as I much have.