I just received my Eberlestock X2 about a week ago. I haven't put it through a hunt yet, but I did take it over to one of my hunting spots, unbuckle it, put a 50lb bag of corn onto the back, buckle it all back up, and mount the pack to my back. After adjusting for proper fit it was pretty damn comfortable, and I went half a mile through some uneven, scrubby terrain to deposit my 50 pounds of corn into a pile that I put a trail camera over to spot some hogs I believe are running around. It certainly feels durable so far, and while it will cinch down nice and small when needed, it expands outward and carries all that I'll need for a day hunt, with the ability to strap camp supplies to the outside for a longer trip if I'm two-manning it.
Alternatively, keep an eye on Camofire.com and see which of the Mystery Ranch packs you like, such as the Crest or Pintler. They've been re-running the same sales every few days and probably will until they're sold out.