Tom,
I've only tried the Ohm 1.0. The Ohm 2.0 is better, but it still exhibits the two problems I mentioned.
Jennifer,
Maybe the Gorilla works different for you, but it carried absolutely awful compared to other better-built suspension systems that I've tried. And yes, I did own the Gorilla briefly (the latest one).
Here's a simple test I use to determine pack load transfer:
1) Load the pack to some of the heavier loads you'll carry.
2) Adjust it to best fit your body.
3) Loosen the shoulder straps
If the very act of loosening the shoulder straps causes the pack to rotate away from your body, it's a very poor design. The better the suspension system, the more you can move around before the back begins to rotate away from your body. A pack with a curvature built into the pack and good stay and hipbelt attachments will balance the load more forward and distribute some of the load across the various parts of your back. Overall, it will be more stable when under motion and exhibit less strain on your shoulders and trapezius muscles.
Of course, just because a pack does a good job at this, doesn't mean that it has a good suspension. However, it's a relatively simple test that clearly demonstrates the poor suspension design of every UL framed pack I've played with.
Another quick visual test that sometimes works: when a pack is adjusted correctly, are the top of the stays and load-lifter attachments more forward (in the vertical plane) than the hipbelt? Or are they directly above the hipbelt? If the latter, generally the suspension won't work as well. The presence of a lumbar curve when packed is also a good indication of a good suspension system.
Drew,
Based on your description, I'm definitely intrigued by the Arc. At the very least, it sounds like it'll definitely work better than the other UL framed packs.
Kate,
Packs with good suspension systems?
The Mammut Lithium 30 actually has a really nice frame design that carries very well and is actually sub-2lbs. You'll want to bend the frame a little bit to fit your back. Honestly, I think this design is the one most adaptable to UL framed packs. I tried to get Zimmerbuilt to make one with a similar frame design, but he refused to stray from his own framed design which, as described to me, is really no different than GG/SMD/MLD frame designs (crap). It turns out he's more of a semi-custom than a true custom shop.
Many Black Diamond packs I've tried have very good suspension designs. I especially like the Demon (caveat: if the framesheet fits your back). Black Diamond is really close to having really good UL designs. The materials are a bit too heavy though.
Many Osprey packs have good suspension designs. Of the Ospreys, my favorite is the Kode snowpacks – they carry skis exceptionally well, which is a very challenging job for any suspension. I'm not particularly fond of the Hornets or Talons. The Talons are actually exceptional for lighter loads, but tend to collapse when you get into the 20-25lb range. If the framing of the Exos fits you, I'm sure it would be an exceptional UL framed pack.
Deuter makes some good suspension systems, but they're pretty heavy duty and overkill. If they paired down the overall overbuilt-ness of the suspension system, and chose the right features and fabrics, they could make a killer UL pack.
