Most are fine. There are some problems but for the most part, they have been fixable. No huge number of unfixable vehicles. The most common problem is the brake rotors warping. Nissan redesigned the part and will replace them for free with the new parts so don't worry about those. If from a private sale, ask for maintainence records and what they've had done at the dealer. If from a nissan dealer, I'd have them do the TSBs on it for '04.
What options, miles, how much, etc. We can tell you if you are getting a good deal or not.
BTW, its the BEST full size SUV, period. (Except for gas mileage)