A low car is a cool looking car. When a car has been lowered the tires fit better in the wheels wells, the contours of the body flow more smoothly when they float just above the ground and a low car has the look and feel of a racecar. Lowering you car will also lower the car's center of gravity by a corresponding amount and this will increase cornering ability.
But lowering you car has some potential problems that you may or may not have thought of. Problems like potholes, speed bumps and driveways. Quickly you will discover why the manufacturer sent you car out into the world with that seemingly high ride height. Racecars can get away with a super low stance because the racetrack is relatively smooth compared to the real world of the public highway.
Reducing ride height by lowering your car may also reduce suspension travel. Instead of a comfortable ride, your car may bottom out on even moderately bumpy roads. Bottoming can negatively affect your shocks and struts, increasing their wear and shortening their useful life. And if you reduce your ride height through lowering you may need to use shorter stiffer springs, which will give you a choppy, harsh ride.
Another problem with significantly lowered cars is the problem of getting a floor jack under the proper jacking points. You can not just slip a jack under any old spot on the car's body; you can do some major damage to your car by trying to lift it in the wrong spot (check your owner's manual for more details). And it may also be possible to "high center" a car that has been severely lowered.
But the most important consideration when lowering your car is the effect of lowering has on the suspension geometry. Back in the days when a car's suspension was hardly more sophisticated than that of a coal cart, lowering the car down on the wheels was very straightforward. But today's cars feature intricate suspensions that are dependant upon the car's springs to be a particular height so that all the other components will be in their proper relationship. Lowering a car can affect the tire's camber (the amount of lean of the top of the tire toward or away from the car) and toe (is tires can become pigeon toed or splay footed) and will need to be corrected with new alignment and in many cases new parts to allow adjustment to get the tire alignment as close to normal as possible. Not correcting your car's alignment will result in increased tire wear as well as negatively affecting steering response.
And in some cases, lowering your car will result with your tires rubbing on the bodywork of your car, which will need to be corrected with cutting, hammering, or flaring of the wheel arches.
If you must lower your car, consider moderation and be sure to include the purchase of camber correction and alignment into your cost estimates.