If you are a fan of Mario Kart you don't really need to read much more. It remains as good as it ever was. If you need a bit more convincing, trust me it is excellent. The graphics are about as good as the DS can manage and they look superb. They're sharp and colourful and fit the style of the game perfectly.
The gameplay is and always has been MarioKart's strength and although not much has changed since previous incarnations, it remains very addictive. If you get the chance to play it against others, be it over the net or just against someone nearby, it can really take over your life.