Great to have with friends, but Single Player mode is Repetitive, with a capital "R".
However, there are many realism problems. First of all, enemy carts NEVER fire shells. Also, getting in 5th or worse makes you retry the course, which doesn't make you "equal" with the rest of the players. Additionally, there are VERY few unlockables, as Mirror Mode is just about it.
Mario Kart Double Dash, on the other hand, fixes all of these problems and despite the fact it doesn't seem as "classic" looking as this, it definitely knows fewer boundaries.
But I have to admit that muliplayer has been and is probably still quite fun.
P. S. Record time in Wario Stadium for me: 56 seconds. Best lap: 5.5 seconds.