I bought a Mountainsmith "Day" off ebay - I really wanted to see what all the fuss was about regarding these packs.
My use will be wading/fishing/hiking in to remote spots or walking up streams to fish. I will carry all I need to spend the night if I have to...and some light tackle. In the past, I've used a backpack, but for the few items I carry, it almost seems overkill. So I bought the "day".
As to the lower strap hook up...I've used this style of attachment for other things before, so I knew to just turn the figure 8 part sideways and slide it thru the rectangle part already on the pack. This really makes an extremely strong connection that will not come apart. We used these type of connections in the military. Both sides are pre attached permanently, hold really well, and come apart easily. Once you do it once...it's hard to imagine ever having a problem taking them off and putting them back on.
ok, so...my pack now? with the strappettes? AAAAHHHHH... :) I think the primary advantage is the overall displacement of the weight between hips and shoulders.
The straps seem very well made, they are pre-curved, and don't seem to dig in to my shoulders at all. Time will tell if I stay with this set up - but early results are good for the "MS Day" pack...especially with these strappettes.