I have a 2003 WJ with a 4.7, I have had it 7 months and it has 98,000 miles. I've had 4.0's before and I like the pep from the 4.7L. My Jeep also has a select trac transfer case so I have more options than the Quadra Trac models. The select trac is a wanted option, many people swap out their quadratrac t-case for a selectrac. So far I have had no problems, I've put about 4,000 miles on the Jeep. I wouldn't listen to people that say "stay away from a particular model, engine, brand" unless they can back it up with personal experience. Most of the problems listed above are what I would consider typical for a high mileage vehicle. Any vehicle you purchase with those high miles could crap out, its dark side of buying a used vehicle with high miles.
I have had several Jeeps.
a '99 TJ SE with a 2.5L, I had no engine problems.
a '00 XJ Sport with a 4.0, the head cracked and I got rid of the Jeep.
A '05 LJ with a 4.0, no problems, I traded it for the WJ after we had a kid.