You also won't get any feedback through the car on that side (ie you wont feel the bumps) thats if you own a Sport model.
I can generally tell when I have under inflated tyres on a car by the lack of feedback. Its difficult to describe but if you run over a drain or a crease in the tarmac that you would/should have felt, you just don't get the feeling through the steering or seat if the tyres are under inflated or flat. But this doesn't help if you find this out 2 miles down the road!!