I drove my truck welded on the street for about 15k miles. Rear tire wear is greatly increased. You'll notice it most in parking lots, just from the scrub and a little bucking at times. Faster than 15 mph on the street driving like most people doyou won't be able to tell. For me it wasn't worth the $$ as big tires are expensive, A locker was less than a pair of tires.
On a track car it will induce alot of understeer in slower corners. It kills me in slow turns. The faster the turn the less push. If you have alot of power it is better than an open diff for getting power down on corner exit, reason why I did it. A low HP car wouldn't see the same benifit. On a street car I would only do it if you run cheap tires and don't have the $$ for a LSD.