You cannot get any higher on DSiWare.
Level design is textbook perfect with multiple routes, secret shortcuts, tunnels, tight passages and open spaces. You have 12 tracks altogether (6 lvls normal and inverse - and it's really like night and day) and each one of them looks completely different. It takes time to figure out your best (or just favorite) route but it's so much fun when you leave all the others behind after an inch-perfect shortcut dive. Well done.
Graphics, as it was mentioned, look to good to be true for a DSiWare game, music/sound is ... decent (it's there) and AI is more than challenging when you switch game's difficulty to Veteran or Ace (totally Mission Impossible).
Power-ups add extra arcade spiciness to regular racing. Missiles and speed boosts (triggered with L/R) can turn the game around in seconds and when you learn to dodge enemy rockets you feel like the king of the skies. Tasty blend of fast racing, shooting, dodging and constant pressure from your opponents makes (almost) every race a thriller/joy ride.
All things considered, 800 points is a bargain, and AiRace deserves all the praise. Maybe I don't have much DSiWare experience but this game really is something I'd love to get back to after months (or even years). One of the best DS games I've ever played (racing fan - bear in mind).
9/10 with button controls. 9,5 when you learn to use stylus.