[garethsprice]

Agree on the cleanliness - most cabs are fine. However, try getting a yellow cab from Manhattan to Brooklyn after 9PM, especially in a popular/busy area.

Anecdotally I'd estimate there's a 1 in 3 chance of the driver either driving off/refusing the route, having a "broken meter/card machine", but will take (a large amount of) cash or (if you appear to be from out of town) taking a ridiculously long route.