As I tried various packs I suprised myself and ended up with one of these:

http://www.eberlestock.com/introducing_the_x__project.htm

It seemed to meet the needs I had for a daypack and I'll hike out to the truck and get my Frieghter Frame sans pack for the rest of it. I'm finding that I'm carrying more and more as I get closer to my desert deer hunt saga. Shooting Sticks, Binoculars, GPS, Water Bladder, and Binocular Tripod make up the essentials, besides gun and ammo. I always carry a knife and a handgun with reloads, as well as a flashlight, and cell phone of some sort so that wasn't included in the "essentials".

The more I play with the pack the more I like it.

Biker

Those Eberlestock packs seem like good packs and seem to have the features one would look for in a pack. 

One thing to always consider in any daypack or backpack used for hunting is how quiet the overall pack is.  Many packs have too many zippers than clank and rattle, or numerous loops and straps that get caught and hung up in the vegitation, etc.  Plus I can't believe what some of these camo hunting packs cost these days, way more than most hunters used to spend in the past on such stuff and surely way more money than I care to spend these days too, considering what I've been using.  I guess there are just some thing that I don't need to be camo'd, especially when rifle hunting.  Besides I only bring along a few essential with me when in the field actually hunting anyway. 

For a daypack in the field I've been using an old basic Jansport backpack that I bought years ago at my college campus book store.  It's worked extreamly well for me over the years, and with the exception of having a well seasoned appearance it shows very little wear.  It's not too big or bulky, yet it's roomy enough for all my few essetials, the cordura is broken-in enough to be relatively quiet.  The only modification I made to it was giving the zzipper grips a moderate coat of rubber sole cement to dampen and lessen the metal to metal contact from rattling too much. I don't think I paid more than $29 for it at the time.  Some people today may say that a pack like mine just doesn't cut it in the field.  Well....I can't say what's best for others, I just know what's worked for me. If I'm close enough to the truck I can always go back to retrieve my pack frame.  If I decide to venture farther then I wear my pack frame while hunting.