I think you've got a pretty good list. Packs are unusual, in that it's not just dead weight. In other words, if you change your sleeping bag, and get one that is 8 ounces lighter, your load will feel 8 ounces more comfortable. However, the same isn't true of a pack. You could get something 8 ounces lighter, but it might feel less comfortable (for your load on your back). Also, if most of the weight is in the frame, then there is almost no torque involved, which means it is less taxing than weight that is further away from your body.
I think the packs you mentioned are good compromise packs -- they provide a decent amount of support for light weight (and more than enough for ultralight) backpacking while being fairly light. I think you won't go too wrong with any of those choices. If possible, I would try them on and compare the comfort with your set of gear. Since you are just starting out, try borrowing some stuff from people. Other than that, consider the various features. Personally, I like a minimum of bells and whistles. That way, most of the weight is in things like the frame and hip belt. I use the Vapor Trail, which I believe fits that description (although I would like to change some of the fabric choices to shave a few ounces). As I see it:
Granite Gear Vapor Trail -- Good solid pack.
Granite Gear Meridian -- Same size and frame as Vapor Trail but adds the removable fanny pack (your choice as to whether it is worth the weight).
Granite Gear Latitude -- Same frame as Vapor Trail but has a different loading system (your choice as to whether it is worth the weight).
Personally, of the Granite Gear choices, I would go with the Vapor Trail. The removable fanny pack isn't worth it to me (just use the VP when base camping) and frankly, I prefer the simplicity (not to mention weight savings) of the roll top. Of course, I might be missing something about the comparisons.
I'm not sure about the Osprey packs. It seems like they have too many zippers and extra straps (which add weight). They do seem to have put a lot of effort into their suspension system though, so if it has paid off, then that's great. Within the range of light or ultralight packs, I think the key is which is more comfortable for you.