A:Oh, those all are nice packs, Mike. Obviously all about the same size: 70 liters (4,300 cubic inches), good suspensions, and hiking-friendly designs. The Gregory Baltoro ($230) is a trail classic, a very rugged and fairly heavy (5 pounds 9 ounces) pack that has all sorts of lash points, a sleeping back compartment, and zip-through main bag access. I have an Osprey Aether 70 ($259) and like it very much. It's a little bit lighter than the Gregory, but has a similar packing-friendly design. I haven't used a Deuter Act Lite 60+10 ($189), but it has a classically European look—very clean.
One thing I like to tell people is that the weight of a pack can be a misleading feature. Some packs are indeed light in weight. But if they don't support the load well, 40 pounds in a four-pound pack is going to feel four or five pounds heavier (or more) than the same load in a six-pound pack.
Which brings us to the REI Flash 65 ($169), a pack that offers 4,000 cubic inches of space yet weighs just a touch over three pounds. And I think it's very competitive in this pack range. It has a very good suspension that is more than up to loads for three-four day trips. It's not a huge pack, but it has lots of packing options and over-fills pretty easily, if need be. Durability is good, but not quite on par with the much heavier Gregory.
I'd say the REI is ideal for loads up to 40 pounds. At around 30 it really shines. Heavy loads can make it sag a little. But in this day and age a gear load for a multi-day hike need not weigh more than 20 pounds, minus food/fuel/water. So if your shaving weight and carrying a lighter load as well as a lighter pack, then the REI really fills the bill.
Hope this helps!