This car is bulletproof. Let me put it to you this way, it was the first car for 3 different teenagers. I was one of them, the engine was redlined almost daily from day one, shifted the automatic like a manual when we felt like it, in 2wd mode it does burnouts for days, and I personally drove it through a river that caused water to go above the headlights briefly... and this little SUV has never missed a beat.
I was also working as a part time technician at the Infiniti dealer, so I did most of the maintenance on it, and even THEN I missed a scheduled oil change or two out of laziness. But this car simply will not die.
My parents refuse to ever get rid of it because it is the only car to not give them a headache. So if you want a reliable, safe, good all weather used car for your kids to beat up and you not worry about... get a QX4 or a Nissan Pathfinder of the same year 2001-2003. These were the best years for this model, because it has the MUCH improved 3.5L V6.
Another big reason why this engine is better is not only it's 70+ more horsepower than the old 3.3L... the 3.5 doesn't have a timing belt... so all you have to do to it is change the oil and maybe new sparkplugs at 100k or so... That's IT!
The only other maintenance issue with these models is that they go through front brakes relatively quickly, every 25k or so... but I think it's a fine tradeoff considering how durable the rest of the car is.
I predict after a nuclear winter, the only survivors will be cockroaches, and Infiniti QX4s.