Mickey's Speedway USA was among the very first 3 games I got to play in my life along with Pokémon Stadium 2..and Mario Kart 64. I enjoyed it alot...17 years later...3 year ago from now..I now have my own Nintendo 64 w/ MSUSA. Now I have purchased the GBC version, can't wait to try that.
If you already had the save data, I don't consider it cheating though. I agree that Mickey's Speedway is among the best kart racers for sure, I give the edge to Mario kart though simply because I have a bigger attachment to the characters but I also feel some of the levels have more 'height' to them. One of my all time favorite kart racers is Sonic All Star Racing Transformed, I love how there are so many cool Sega characters in it and it has great level design, what I love most though is the seamless transitioning from car to plane to boat.