Okay, some parts are really well designed and others are horrifying. To start, the game needs a working preloader. Probably lose many views and cost you ratings with it the way it is now. Also, the "start game" button is oddly placed, as though to encourage mistaken visits to website. Slightly enraging.
Next, the controls are really sloppy. The car is frustrating to control, and feels cramped and unexciting. However, I do really like the animations for the car rocking to and fro when it moves. Pretty cool detail. However, the 3D guy is ugly, and so is the title screen. Good looking levels are cars, though.
I agree with others that some of the sounds are either dull or just too grating.
Now, speaking of the levels, it is annoying to get almost to the finish line or target parking spot only to bump ever so slightly into a wall for an instant "GAME OVER". Perhaps there should be an acceptable threshold for car damage due to crashes based on speed or what you hit or whatever.
okay, so...out of 10...
gfx - 9 (great cars)
sfx - 4 (grating sounds, also needs music)
design - 6 (frustrating to start over)
gameplay - 7 (taxi controls feel sluggish)