I'd argue it's a good system if the salesman specs it to the right application.
We never had a frame crack on the trucks we ordered. I'd guess if anyone could bust one it would be a Michigan Log Train. The installs were on CL733's, long bed with Serco 8500 loaders, Cummins ISX, Rockwell full lockers, double framed, with a pintle plate closing the rear of the rails. The log racks were unitized w/8 point attachment and not free standing cribs, so that also adds frame strength via the one piece bed. On the other hand the amount of roll-over stress on an "Axle-up" turn should have still been able to break the frame if it was capable? IMO-Bouncing through the woods down a frozen snowmobile trail, for miles, with an overload constitutes a proving ground.
Axle cracking is the real issue with the heavy set-ups. I've seen guys in the shop with the same truck set up (as above) and Hendrickson Z-member (loaded) air suspensions pull up their pusher & tag axles and the "Z" became a flat "------" under load. Those guys usually would crack the axle housing under the Z spring support pedestal. Camelbacks and Raydan grab a lot of the axle housing at the anchor points so they never seem to crack it. The Z spring guys also often get water in the axle before the cracks are found (hidden under the receiver), so now your putting a bearing kit in the diff while your fixing the spring pedestal cracks. Eventually Mack made a weldable Z-pedestal and less cracking happened.
The crux of the issue with heavy vocational is axle tunnel crush from the spring u-bolts being compounded with overload on the same area of the axle. The U-bolt is pre-crushing the axle tube on the same spot your load is trying to snap the axle housing at. If your overloading you want a suspension with no u-bolt distortion, only weldment attach points. Camels and Raydan don't crush, so now your tunnel isn't being distorted before the load is applied.
I had to pull the main members on one Raydan and re-bush the forward eyes on each side. I was able to do it with no special tools beyond our press. I really like the set-up. Simple, Beefy.
I wonder if the salesman may have witnessed breaks with a Canadian Spread, if they make them? That would compound the front anchor twist against the frame esp with a shorter turn radius truck.
They say you can run it uninflated if you blow a bag or have an air problem.----I'd guess you will also get less axle tip and less driveline vibration when the suspension of the link goes flat?