I find the Pinnacle great for ULers who have more volume than the average UL hiker. For instance, I carry a hammock, which, when combined with 2 quilts, takes up a lot more volume than a tarp and 1 quilt.
Make no mistake, this is an UL pack and not a stepping stone. At 1 lb 10 oz, it's just 3 oz heavier than its smaller cousin, and pack that is sometimes synonymous with UL hiking, the Jam2.