I recently bought a 2004 TJ Sport (Columbia Edition) and although I have only had it a few months, I really like it so far. Many car magazine reviews say the TJ is uncomfortable and noisy. OK, it isn't a Lexus, but the bucket seats are excellent, the ride is smooth, it has a tight turning radius, good visibility, is highly maneuverable due to its small size, and it is a ton of fun to drive on anything from highways to washed out logging roads.
Concerning unknowns and problems: First, for some reason I am not sure of yet, my Jeep came with window stickers claiming 19/26 mpg for city/highway driving. According to the EPA, it should be 16/19. In practice, so far I have gotten 19/23 – I am hoping to get close to 26 mpg on the highway after the engine is fully broken in (3200 km so far). The 4.0L inline 6 is very responsive and smooth, but my jeep does not have quite as much acceleration up steep grades as one might expect for such a big engine. Based on these observations, I am guessing this model may be geared tall - this would conserve fuel and decrease the maximum acceleration in a given gear. The control layout on the dash is a pretty archaic (why do you have to dial through the A/C to get to the fan only?). Also, make sure you have someone with decent strength to help you change the tops. It's pretty much impossible to do alone.
There were no mechanical problems at all with my new Jeep. The only issue was that the manufacturer had failed to properly seal the A/C so it was delivered without any refrigerant. The dealer replaced and tightened the fittings, no problem since.
In short, this Jeep is a ton of fun – it has made me enjoy driving again. You can take it anywhere and it is so tough you hardly have to worry. I have even gotten the roof muddy on the way to a hike in the back country – in what other new vehicle besides a jeep would you do this and not care? As an amazing bonus, in this model the fuel economy is quite respectable.
Last comment: now that I finally have the Jeep TJ I've always wanted, I begin to notice how many people own these vehicles for status only. You see kids cruising around town in shiny new Rubicons (no doubt purchased by rich parents), which probably never see anything off the pavement. Jeep as a status symbol: BAD (and stupid). Jeep as a great all-around vehicle to get you places you could never otherwise go: EXCELLENT.