I bought this truck 9 months ago with about 149,000 miles. It now has about 154,000 miles on it. Only had one problem besides a couple minor things. Even though it was never a real problem nor was it noticeable, the transmission had to be rebuilt. Also had to replace the clutch from normal wear. It was the first time it was replaced. Very reliable and has amazing offroad capabilities. Poor gas mileage though. I only get an average of 13-15mpg depending on how and where I drive. Other Xterras tend to do better I think. It is also a little sluggish. Also I am 6'5" and I fit just fine in the drivers seat.
Favorite feature is definitely the 4wd. The owner I bought it from just put new mud tires on it. And let me tell you it impressed not only my friends but myself as well. Almost everything else on it works great.
If you are looking for a very reliable truck that you can take off the road then this would be perfect for you. I've never towed anything with it yet except when my Ford F250 couldn't pull a trailer out of the mud, even with 4wd and decent tires. I hooked up my Xterra to it and no problem! Trailer came right out of the mud.
Gas mileage and power are really the only things that need to be improved. Also it would be nice if the steering was a little more responsive but it really isn't much of a problem at all. I'm quite happy with everything else on it. If you're looking for something with more speed, then you shouldn't even be looking at SUVs.