I've got an '04 Titan that I bought new. No major issues in the 130k I've put on it, it's done everything I've asked of it and then some.
The issues that l've had, that sound pretty typical for the truck...
Replaced the radiator due to a cracked plastic tank
Exhaust manifolds replaced under CA emissions warranty. I believe These were updated and less prone to cracking in later years.
Clearcoat did not hold up well (dark grey color), and the paint is very thin.
Fabric seats not very durable.
HVAC actuators wear and get noisy.
The brakes had an issue when the truck was brand new. The pads were replaced under warranty at around 5,000 miles, no problems since. I was told that the original pads had a problem with the compound. Nissan fixed this early, but "bad brakes" seems to have stuck.
No problems with the rear diff. Nissan replaced the metal diff cover with a finned aluminum cover and the newer spec heavier weight synthetic gear lube in '05. I've done a good deal of towing.
The good-
The drivetrain is bullet proof. And makes plenty of power, actually makes the big truck fun to drive.
Huge amount of room inside the crew cab . Can fit lots of cargo inside with the seats folded against the wall. Very comfortable for long distances. Drives terrific for a large truck, much better than the Ram and GM trucks of the period IMO.
That sound! Even with the stock exhaust, it sounds terrific.
If I ever replace it, I would really miss the adjustable cleat and rail system in the bed. Why doesn't every truck have this? Makes securing the load a snap, and makes transporting big awkward items possible.
This was the first truck with stability control available, with towing stability in mind. It saved my rear when I was towing a car on a rented trailer that turned out to have defective brakes- on one side.
I get all of the LS love when it comes to swaps and mods. But in a truck of this era, that vintage LS couldn't hold a candle to the Nissan 5.6. Some of the credit also goes to the transmission, which was also much better than the ones in the other trucks at the time.