I suspect that down the road, the 5th gens will be as problematic as the 4th gens. The reason you don't see as many issues on the 5th gens yet is because they're still new and nitrogen filled. As these trucks get older and higher mileage, the airbags tend to crack and the seals in the system deteriorate and begin to leak out the nitrogen. If you can keep nitrogen in them, they'll be virtually problem free. That sounds easy, but it isn't.
The issue lies in the fact that there are so many common leak spots. I see it all the time - guys have problems in cold weather and take it in to the dealer. They replace (usually) the compressor or the valve block, refill with nitrogen and send them on their way without actually fixing the leak(s). A couple months down the road, all of the nitrogen has leaked out and you're back to freezing up and malfunctioning again. When the system freezes, it tends to substantially reduce the life of the compressor as these are very low duty compressors and will overheat in less than ten minutes if run constantly.
If you want to look at fixing all of the leaks, you'd better have some deep pockets. The bags commonly leak around the clamps and sometimes are hard to diagnose as they may leak in certain temps and not in others. There are 15+ o-rings in the system. Every time one of these leaks, you're looking at replacement cost on the parts plus ~$300 to have the system refilled with nitrogen. The price on compressors has come down substantially in the past 3 years but they are still $800+ from the dealer.
On a 5+ year old truck with no warranty, it makes a ton more sense to convert to regular suspension unless you really have a need for the air suspension and don't care how much it costs. There are some great resources for this, like
http://airdelete.com
