As noted, you won't find a UL pack at REI or any big retailer. And a UL pack may not be a good choice unless you go all out with UL gear.

My favorite pack is getting worn out and I also keep looking at the Zpack Arc Haul as a replacement. I'm not a fan of frameless packs. But if I get an Arc Haul, I'll also want to get a cuben fiber tent and rain jacket, a quilt and new pad. And a down puffy. Now I'm in the hole for close to 2 grand. But it would be a little easier to carry then my current load, which typically runs a little over 20 pounds with 3-4 days of food and a little water. I guess I need to see how much spare change I can scrape up over the winter. Unless everyone who reads this sends me $1.00