I could not be happier. The step up between these Ions and my old Rulers is incredible! Almost as nice as stepping up from Sorels with a scavanged ski boot liner stuffed inside to the Rulers.
Based on the Burton flex scale, I was worried these would be too stiff. I ordered new Rulers (my old Rulers were nearly a decade old) in the same size for comparison and fell in love with the Ion. The Ion is slightly stiffer... but it's also a much more progressive flex compared to the Ruler.
I went a half size down from my street shoe size of 10.5... could have possibly gotten away with a full size down. I wore the size 10's in extreme discomfort all day at work on Thursday, hoping they would pack out enough for a FridaySunday Mammoth trip. By the end of the first day they were comfy... by the end of the trip, almost TOO comfy... wondering if I should have gone with a 9.5 to eliminate ALL wiggle room.