Having been a lifelong Seattleite (we do call ourselves that), I've seen McHale packs float by on the trail and sold in used gear shops, even a few at garage sales and thrift stores. I've equated them with Dana packs as bomb-proof load carriers, expensive and long-lasting, but not in the ultralight scheme.
If I were in the woods professionally and carrying heavy equipment like a scientist, photographer, or climber might, I think packs of this type would be more comfortable and durable. But I'm not thinking of UL loads or equipment inventory at all.
There can be a big difference between building an UL pack with a couple stays in it to improve load transfer and a pack with a full-blown harness and stays, with the UL pack and stays bridging the 20-30 pound gap and the bomber packs aiming at 30+ pound loads— huge generalities here.
The trap is the same as it always has been– heavier materials and adding pockets, zippers, straps, big buckles and all the rest, driving pack weights up.
On the other hand, getting a custom made pack that fits well is just like getting custom made boots– a fantastic luxury that makes sense, cost aside. Make sure you compare apples and apples there. Using cameras as a parallel, you wouldn't expect the same results from a $200 point and shoot as an $1800 DSLR. I would expect much more from a $600+ pack than my $150 mass produced rig.
On the UL side, there is a big difference between packs that are basically a stuff sack with shoulder straps and a well designed model with shoulder straps and waist belt that transfer load and fit properly. There are those SUL Spartan rigs that throw a lot of comfort and durability to the wind in the name of weight savings. Make your choices and live with the compromises— no free lunches served!
Now wouldn't it be interesting to take McHale's or Dana's knowledge of fit and load transfer and do a SUL tweak? Yowsa!