I've also been in the hunt for a new pack with a similar capacity, and here's what I've found. Keep in mind that I'm a totally newbie when it comes to lightweight packs.
Granite Gear Blaze AC 60
Pros: Best suspension, adjustable for fine tuning torso fit, bought at REI-convenient if there's a problem, 60L for lots of storage, all around great load hauler.
Cons: Heavy - mine comes in at 48 oz with added MLD hipbelt pockets, no hipbelt pockets included, mesh pockets prone to snagging.
The following are the packs I have so far tried. Don't take too much stock in my opinions, as I never tried any of these packs in the field, mainly so I could return the packs while only eating the shipping.
Gossamer Gear Mariposa 2012
Pros: Excellent fabric, most comfortable back panel(sit-lite pad), lots of great pockets and storage, very comfortable with light weight (~20 lbs), comfortable hip belt, looks great, found the pre-bended stays to contour nicely with my back.
Cons: aluminum stays are not very sturdy at all, hip belt is only connected to pack by single strip of Velcro - leading to serious weight transfer problems with heavy weight (30 lbs), didn't like top closing pocket (too much fabric without much purpose), had an odd problem of the hip belt buckle constantly loosening, load lifters seem to serve no purpose - they are not connected to the frame but rather some fabric on the hood.
Conclusion: The suspension problems were really too much for me to overlook. When loaded (>25 lbs) the pack did not seem to move with me (very bad sagging at the hip belt) and pretty much put all weight on the shoulders. I would guess this pack works for someone who keeps weight down and takes extra care to pack the bag properly with a rigid sleep pad.
ULA Ohm 2.0
Pros: Excellent fabric, awesome hip belt, connection between pack and hip belt is solid, great pockets and overall lots of excellent features, load lifters actually connected to frame.
Cons: I again found the stays to be very flimsy - the suspension was overall much better than the mariposa - but does not have the innate rigidity that I'd like - tried cutting a ridge-rest to replace the foam backpad but didn't find much improvement, don't like the top closure cinch mechanism.
Conclusion: The suspension problems were lessened, but still ultimately a problem for me. I would think this pack is awesome for approximately 25 lbs or less.
Pros: The best stays of the lightweight packs - much more rigid - nicely bent to back shape, the fabric seems durable, best suspension due to sewn in belt and straps between belt and pack, very comfortable hip belt.
Cons: the least amount of features (by design of course), backpad is not removable - not sure if the fabric will be uncomfortable if sweating a lot. Definitely the most expensive, even more so if planning on adding pockets (at what point does one just go for a Mchale?).
Conclusion: I'm going to keep this pack as it saves me roughly 16 oz and appears to have superior load hauling capability, not sure if it will be as good as the Blaze. I like the dry-bag simplicity, but will probably add the back pocket and bottle holders should they become available.
Well that was pretty wordy, I would prefer to try out the zpacks before making my final decision, but the money spent shipping back and forth is starting to equal a pack itself!