I considered shackle reversal for a while, a long time ago. The problem for me was it seemed like it was going to be a decent amount of work and it would definitely have tradeoffs. Such as needing a longer driveshaft, nosediving on braking, and it might upset my ride height making the front end taller and require me to do something out back to even it out to get me back to level or some rake, since I don't tolerate any squat. There were no good bolt on options and the weld on fabrication type options requiring making permanent frame changes that I didn't want to make.
The only reason I really wanted it to begin with was for road ride quality, since they claim the bumps are less jarring. Personally I think it's mostly marketing hype. It might make a really crappy set of springs ride better, but honestly, with good springs like what OME sells, bumps with current shackle setup are not jarring at all, so I don't think you need to have shackle reversal to fix that problem, just better suspension components in general. As for offroading I could see both setups having pros and cons.