hipbelts kinda stink for women with actual hips. most belts are sewn on somewhat straight, since men mostly have straight hips. but for women they really should be sewn at an angle - so that they cup the hips. the other problem is the small bump of abdominal padding that most women have - the belt tends to ride up and sit on it, which is less than comfortable (for me, anyway). in my fantasy world, the belt is stiff, cups the hips, and is canted downward in the front, to rest on the abdominal bum instead of riding up over it. this of course increases the weight of the pack...
i haven't used many of the more popular UL/LW packs. i do have a women's REI UL 45, which is not the lightest pack around but I have found to be very comfortable. sadly, the best hipbelt i've ever had was on a pack that weighed over 6 lbs empty - the Gregory Electra (but if ya gotta hump 50+ lbs it's awesome).