For me the waist belt is just about right for day use. Material is way to damn hot, but size seems just fine. I will be happy when they put as much thought into the waist belt as they did the rest of the pack. But, until then it works ok. My day pack is usually a Blacks Creek Western. Love that pack!!! The Exo 3500 compresses better and actually rides nicer as a Day Pack than the Western does. Exo is just a little noisier and a little harder to get under branches when your fat and stiff like I am.
If you want one "do it all" pack...this Exo seems about as good as any I have tried. Oh, and DANG is it nice and light!!! Lighter than the two 5200 Kuiu Icon packs I've tried. Other than the cheap waist belt I'm liking it much more than those two! I've never played with a Kuiu Ultra so can not comment on that!