Fun, for a while
Crazy Taxi was a fun re-release of an arcade game. It's fast, and it's fun, but I personally did not find it to have a great deal of staying power. I don't mean that it's bad, just that it got old.
The game starts out strong, completely deserving of the name "Crazy Taxi". You drive around with a blatant disregard for all laws and personal safety, and the game does have a lot of pick-up-and-play appeal. The general feel of the game is a bit out-of-control.
Driving around all nuts is fun for a while, but it starts to feel old fast. I played it for about a month, and then found the game repetitive and dull. Pretty much all there is to do is either drive around picking up people, or doing the challenges, which do train you to be a better driver in a way that's pretty fun.
I'd recommend Crazy Taxi as a solid impulse buy to while away some time with, and it's also good if you happen to be entertaining company once in a while. It seems like most people enjoy Crazy Taxi for a little while, but when you buckle down and care less about the crazy and more about doing well, it loses some of it's luster.