Rating: 4 / 5
Make no mistake. This pack has a lot going for it.
As others have pointed out, its 3000 ci capacity is just about perfect for thru-hiking ultralighters. In terms of organizational ability it is feature rich, with dual side bottle pockets, two rear bellows pockets, and a floating lid. The customizable frame sheet is both light and stiff, offering excellent support for a pack in this weight category, and along with a thoughtfully articulated back panel, provides stability good enough for trail running with a full load.
However, the Infinity falls short of 5 stars on several counts. The hipbelt - essentially a pair of thin foam-stiffened wings that wrap only part way around the hips, is too much of a compromise in comfort for the sake of a few ounces in weight savings. And the "wings" narrow to terminate at the worst possible location - directly atop my iliac crest (rather than over the abdomen), causing a great deal of highly focused rubbing, pinching and chafing unless I further pad the area, such as with a back brace as I sometimes wear. Without such measures, I find this hipbelt to be unwearable. A full-size padded hipbelt (with hipbelt stabilizers please) could be incorporated on future versions of this pack, and not relegated exclusively to the realm of the heavier, larger volume packs in the GoLite line offering less appeal to space-efficient ultralighters.
Also, the Infinity's main body is not sized ideally for those with longer torsos (21" in my case). The frame sheet and back panel are too short on the Size Large pack, and the shoulder strap upper attachment points are thus too low. The upshot is that it is impossible to transfer more than about half the pack weight from my shoulders to my hips - a real shame considering the potential capability of the stiff frame sheet to otherwise transfer loads in upwards of 40 lbs. Nor is the frame sheet designed to effect the functionality of the shoulder strap load lifters, meaning that the lifters are resisted only by the pack's virtual frame near the top, an area of the pack bag that is infrequently occupied or otherwise difficult to compress into a stout mass of resistance. Therefore the lifters are quite ineffective at lifting the shoulder straps off the shoulders and compensating for the inadequacies of the too-short framesheet, although they do at least pull the upper pack bag into the back, helping to stabilize the load. To wit, the frame sheet needs to be made longer on all pack sizes in order to make the load lifters more effective. And a "larger large" sizing scheme should be introduced to move the shoulder strap upper attachment points to a higher position for the benefit of those with longer torsos.
As far as fabrics are concerned, the SiLite main body is structurally sound, though prone to puncture as would be expected with silicone nylon. The X-Pac fabric used in high-wear areas is somewhat more durable, but does puncture and abrade more readily than other fabrics often employed in these areas, such as cordura or dyneema.
With a few straightforward modifications, the GoLite Infinity could become a lightweight thru-hiker's dream pack. I sincerely hope the company will consider building upon the strengths of this pack, rather than introducing feature enhancements on packs that lack this core feature set, volume, and target audience.