Did some work on the cooling system over the past few weeks and just wanted to relay my experiences.
The issue started over the winter, when I'd notice that as my engine was warming up it would surge into the upper range of the temperature gauge. It kept it up through the spring, and there seemed to be a relationship between higher speeds and higher temperatures, enough that I'd have to worry for a few minutes if I'd eventually creep into overheating range.
The radiator was in OK shape, but there was a small leak at the cap...enough to drain the reservoir over the course of 6 months or so. I decided to replace the radiator and while I was at it, change the thermostat as I had no idea how old it was, either. I painted the thermostat housing while I was at it, because I had some extra engine enamel and thought I could make some use of it.
Based on some info on this forum and others, I purchased an aluminum radiator off of eBay - made by Champion/American Eagle: Champion 2-row radiator on eBay ($175 or so). I had about an inch of clearance between my fan and the previous radiator, so thought the added depth (2" vs. 1 3/8" or whatever stock is) of the replacement wouldn't be an issue, and I could get more cooling.
Got the radiator and began the install. It was a very difficult fit for a couple of reasons - the width of the replacement was about 1/2"-1" short, and it was a stretch to get it to mount to the grill. Also, the depth of the radiator was way off - it just about butted up to my fan, but I thought I'd have enough clearance for the fan to rotate freely. The last minor thing was that the drain hose came off a central cap and pointed to the passenger side, as opposed to the cap being offset to the driver side with the drain hose easily reaching the reservoir. Managed to get it fired up and sure enough - no way the fan had enough clearance and it was a mess. Coolant everywhere, smoking belts, and a busted radiator.
The eBay company I bought the radiator from has so far been very accommodating, other than making me pay for return shipping. Of course, we'll see how well they honor the warranty and if I get a refund. He gave me quite a lecture on how good his radiators are, aluminum surpasses copper in cooling (BS, but I let it slide), and he recommends people drill new holes for the replacements, etc, but he assured me I'd get a refund.
I ended up getting a radiator that more closely matched OEM from radiator.com, based on a thread over on JeepForum. The radiator took a day to get here, cost me about $325, and was a perfect fit - no struggles, no clearance issues, and it's doing a great job cooling. I'm hovering at about 1/4 on the temp scale at interstate speeds now. So far I'm very happy with it, for the price it was worth it to have a well fitting radiator that does the job right. And it also has a lifetime warranty. I would totally recommend radiator.com to anyone over an aluminum radiator off of eBay.