bonchance, I ride a Soul back to back with a fairly stiff Orange Evo2 alu hardtail. Yes, the Soul is more flexible, but in a good way. It really suits my “let the bike find its own line” style of riding. Works particularly well with my 2.35″ Blue Groove front tyre. Really confidence inspiring.
Obviously, there are loads of other plus points too. Balance and “flickability” standing out.
The only times I don’t like it are on really fast, really rocky, really steep stuff where I wish it was a bit lower and slacker. But then it probably wouldn’t fly through the woods as fast, or be as good at slow stuff. If I bought any other bike I would keep the Soul.