As far as off-roading goes, the tires are the one weak point on a stock JK.
(Okay, there's also the horn, headlights, and gearing on the pre-'12's, but...)
Straight off the lot, your Jeep will go places few other vehicles can follow. But if you're gonna do any kind've consistent wheeling, you'll want different tires. FWIW, I drove a Jeep Liberty through 7 years of Wisconsin winters on the stock SR/A's, and had no problems.