Not just a port but a well built game for the DS.
Stars are what you're after in this game, each level has multiple stars that you need to collect to unlock new levels and ultimately save the Princess from the evil Bowser.
This is the same premises for almost every other Mario game so don't play this looking for any type of engaging storyline.
Throughout the game you can also catch rabbits that will give you keys to unlock touch screen minigames, each of the four characters has different types of mini games that offer a change of pace from the regular adventure.
You may get frustrated at times as you try to figure out how to reach certain stars you can see but not reach. The best thing to do is just forget it and come back to that level when you've unlocked more characters.
I've collected about 115 of the games 150 total stars, and you only require to find 80 to defeat Bowser with Mario.
If you have the time this is definitely worth blowing it on. The graphics nearly match up to the N64 and only a few complaints of difficult camera angles at certain times. All in all a good game, not too heavy in replay value though.