Yeah, these trucks are good, if that's the type of vehicle you're looking for. If you want to build a full-size rig, they are great because they are simple, reliable, Chevy and GM parts interchange like crazy, and there is lots of aftermarket support for them. Check out coloradok5.com
Again - it depends on the type of vehicle you want. I have a 1990 K5 with almost 200k on it, a 1987 Samurai with over 200k on it, and 1997 TJ with just under 100k. All are great vehicles, but very different.
The Samurai is amazing on the trail with very few mods because it is so light. But it sucks on the road because it rides rough and has no power. I have used it as a daily driver, but I will never do that again unless I have to.
It is small and really only fits two people.
The TJ is great because it can be both a street driver and great trail machine. Mine is locked front and rear, with 4.5 inches of lift and 33's. The only drawback I see is that it is still kind of small - the rear seat is out, replaced by a tool box to hold all my trail junk. So again, I can only take two people on the trail.
My K5 has 33's and limited slip diffs front and rear. My parents bought it new, and I got it from them and have owned it for over 5 years. It is big enough to carry a bunch of stuff in it, but not as big as a Burb, and it is shorter than a full-size truck. It is a great daily driver, and it works on the trail too, it is just heavier than the TJ or Zuk. My aunt is visiting from out of town in a few weeks and wants to go with my wife and I to Uwhairre, so the K5 is the only choice because it has the room.
I'll always keep my Samurai because it is too cheap to get rid of.
I'll be swapping in D44s and power steering.
I'm going to sell my TJ, and build my K5 for the trail because I need the room that the K5 has. I guess someone who carries less trail junk could get by with a TJ or XJ.
If you want a trail-only vehicle for two people, I would not get a K5. You can get a smaller vehicle that is lighter. But if you need to fit more than two people, and you like the American iron, I think the K5 is a good way to go. The K5 is even better if you just want mild mods and you plan to drive it on the street too.