I purchased my Xterra in 2003 with 1400 miles on it. It now has 154K and still running. I've had to do a few minor things over the years, new clutch (5 speed), also the fan clutch, belts and a small leak in the windshield I fixed with sealer. But nothing major, Knock on wood. I would love to purchase another Xterra that's how much I love Nissan's quality. I've upgraded some things, running boards, new bumpers, tires.
Gas mileage is good, the style and open feel, yet feeling safe driving it.
I bought it used on a private sale from craigslist replacing my 1985 Toyota 4runner that I ran up 550,000km (340,000miles to you guys south of the 49th). However last year (2011) the in-tank electric turbine fuel pump unexpectedly quit (at 220,000km odometer reading) leaving me stranded on the side of highway. It wound up costing me well over $1000 in towing charges, parts and labor plus an overnight motel stay and a one day travel delay. Now that I know how to replace it I carry a spare fuel pump and screwdriver along with the spare tire....
Great rugged 4x4 that goes anywhere, carries a lot of stuff and comfortably sleeps 2 people in it either on the folded back front seats or by folding down the rear seats. The resulting generous carpeted cargo bed is a great place to have fun in the woods with your significant other... ;-)
(notwithstanding gas mileage improvements) Nothing.
I have a 2001 SE 4x4. Bought it in 2005 with 64,000 miles. 5 years later and now over 175,000 miles on it, we've had no engine or transmission issues with it. I did have to replace an electrical component in the a/c this summer for about $250 but otherwise it's just been routine maintenance. It's a fun truck to drive and very reliable. Not the best backseat for carseats but it is manageable. We're in the process of selling it only because our 3rd child is on the way and we can't fit the family in this car anymore. But that is the only reason we're selling! It's been a great car.
I bought my 2001 Xterra with 73k on the O.D. after looking for a foreign 4x4 SUV it was the least expensive with the best options. I now have 155k on the Xterra and have had some very small things like a slow leak on a radiator hose that took me an hour to fix and $10. But I just had my A/C go out right before summer and we have had several 100+ days that have been miserable. Because of gas prices I want to sell it but then I get to go on a beach, camping or we get hit with a foot of snow and I fall back in love with my baby. This thing is a monster that will get you there every time. Love it and won't get rid of it.