Patagonia's 1200 cubic inch Lightweight Travel Pack was tested as a possible "full-sized" child's backpacking pack for an article coming out in spring 2007. I also reviewed the Travel Pack as an adult daypack; those impressions are provided here.
The Travel Pack weighs a reasonable 11.2 ounces. It includes a top pocket, hydration pocket, and two small, side-panel water bottle pocets. The entire pack stuffs into the top pocket for travel. The hydration pocket is accessible from the outside; however, it's a fairly thin sleeve and a full water bladder will cause the pack to bulge out against your back uncomfortably. Also, the side water bottle pockets are too small for most 2-liter water bottles.
The Travel Pack has a fairly sparse harness. Aside from the 3-D spacer mesh, there is no padding in the shoulder straps. This pack also lacks a sternum strap, and the 3/4-inch unpadded hip belt has to serve double duty as either a hip belt or part of the compression system.
The compression system on Patagonia's Travel Pack is unique. As easily seen in the photos, there is a single webbing compression strap down the front of the pack, which secures the top pocket. There are two additional side-release buckles on either side of the top pocket that attach to the hip belt when the belt is not in use. With these additional straps, the Travel Pack acts as a compression stuff sack, providing 3-point compression to fit those bulky items in your suitcase (it is a "travel" pack after all). For the lightweight backpacker, the Travel Pack could be used as a sleeping bag compression sack, which would then be available as a daypack once camp was established. Personally, I didn't find the compression features useful for lightweight backpacking.
Patagonia's Lightweight Travel Pack is constructed with relatively robust materials. The 30-denier triple-ripstop sil-nylon pack body is slightly stiffer and noticibly tougher than the 1.3 ounce sil-nylons we're most familiar with. The bottom has a 210-denier doubleweave nylon packcloth, which will certainly outlast the rest of the pack. The durable materials make this a great daypack.
The Travel Pack is not a great choice for lightweight backpacking. It's too small to use as an overnight pack, and too heavy to compete as a day or summit pack, carried within a backpack. I also found it slightly too big as a child's backpacking pack. It's best used for day trips or travel, as Patagonia intended.