I had terrible P.F. as well, and had to totally change my footwear. I got myself a pair of Chacos, and I have been hooked ever since. They are by FAR the best sandals I've ever owned - they are expensive, but they wear like iron. I wore out that pair after about four years (I lived in NC - I wore them year 'round just about, nearly every day), and now have two pair of the Z/2's that I rotate between. They are washable, they are infinitely adjustable, and non-marking/non-skid. If they get wet, they never chafe and dry in moments --- they also won't get that funk smell that so many sandals get after they've gotten wet. I've white watered, creek walked, generally hiked and gone all over Disney in them... no other sandal compares for me.
I have Dansko sandals - they are good for work, they don't work for me for TONS of walking.
I have tried Merrells - they work REALLY well for some people, but they arch is no where near enough for me.
I've had Tevas, but I found they wore out more quickly than my Chacos (it's like the footbed gave in or something).
Also! I do have a pair of Fit Flops - the canvasie stripie ones. I do love them for running around town, around the house, even to work on casual days, but I don't think I'd dare a full Disney day with them. They do mold pretty nicely to the foot, tho, creating a decent arch.
There! That's my 2 cents!