With the progressiveness of the leverage ratio curve and my tuning, I've stuck some crazy flat landings from overshooting jumps, with only the slightest bounce and loss of control. The first 4" gives great traction on smoother parts, lets me dig deeper and carve harder in corners since its BB gets really low, and, combined with the stiffness of the bike, really makes me want to do some really crazy shit such as attempting to take impossible turns, coming in excessively hot. The extra air volume and position sensitive damping works well with my bike's leverage ratio curve to make it really plush for the first 1/2 of the travel (from sag, ~42.5mm in, to about 100mm in), which then becomes increasingly more progressive. I wonder if I could find any other STR member that could explain the Boost Valves principles in depth and the advantages it offers. There's plenty of reasons to hate the DHX Air 5.0, but most of those reasons are personal issues. The RockShox also is much friendlier to service, with clear user servicing guides. Other shocks, like the Vivid Air, which has 2 stage rebound damping and compression damping, have damping principles that have been around much longer (speed sensitive damping - high/low speed compress damping) and are much easier to wrap your head around than the Boost Valve's position sensitive damping, where people may find the former easier to tune. Once you learn to tune to 2 different tracks, you pretty much begin to appreciate how nice it is to have extra adjustability over coil or a simpler air shock. You can then tune according to specific tracks. A little patience, adding or taking away a little pressure at a time after some time riding on it, teaches you how the settings affect the suspension's performance. I also doubt people will be successful at getting a tune they like by randomly changing pressure in the air spring or boost valve by over 15 psi at one time.
I doubt people can estimate how to set everything up in a few tries and I doubt the frame maker's guide will work for people on the first go. I might cynical, but I think most people are overwhelmed and are blaming the shock unjustly. You have a lot of tuning with the reservoir air chamber pressure and its volume (via bottom out knob).
The DHX Air 5.0 isn't as easy to set up as the RP23. Works much better for how I want to ride it. Now it's my go to bike for working on my bombing, jumping, hucking, and "gapping" skills. The bike was much more versatile with the RP23, but since I have a high end XC/trail bike, I wanted to cut the "overlap" and make the big bike be a bit more specialized. I replaced the RP23 on my Yeti ASR7 with a DHX Air 5.0, which turned it from a very long legged XC/trail bike into more of a FR bike. You have to go into the purchase knowing what you are getting, else you may be turned off when you find it doesn't work as you hoped.
I also wouldn't consider the DHX Air 5.0 being an upgrade for a number of people and their bike setups.