We had two 4WD Tracker 4-doors, a 2000 4 cylinder and a 2003 V6. Together we towed them almost 70k miles. Great little cars and docile toads. I recommend the V6 over the 4, though the gas mileage is a bit less. More get up and go when more than two people in the car - the difference is noticeable. If you plan to tow 4-down, the 4WD is a must. The 2WD is not towable as is.
We had very little trouble with our Trackers. The 2003 had an Oxygen sensor go bad at 49k miles, but it was replaced under the emissions warranty. And it needed a new battery after 3 years of the 5 we owned it.
If you are looking for a light weight, inexpensive toad, the Tracker 4 door 4WD is hard to beat.