I have been searching for a well-designed, solo tent under 3 pounds for many years. And to replace my REI Roadster, which I like, but it lacks headroom and width. I have been climbing and backpacking extensively for 35 years. Surprised to finally find specs I have been looking for (incl a weight well under 3 pounds), I bought the Big Agnes Fly Creek UL1 and set it up in my basement. Like all modern, name brand tents, it is well-manufactured. Big Agnes got most of the weight out by thinner fabric materials. My micrometer told me that the fly thickness is about 1.8 mil and the Roadster a more standard 3 mil, etc. My other measurements were very similar to the advertised specs.
I used the Fly Creek solo last week in the Sierra's John Muir Wilderness for a five day trip at 11,000 ft. My search ends! It sets up easily, has free-standing stability and was sufficiently spacious inside for me (I am 6 ft tall). My major concern was the thinner materials, but I saw no compromise during the five days of use. Tent walls seem adequate, though I have no way of knowing the effect of years of use. Probably alright, but therefore good ground protection is even more critical with this ultra light tent. Sans fly, about 18 inches of nylon wall kept the considerable night breeze off me, but allowed good ventilation. Headroom is still lacking, but without fly, I sat up to comfortably read with the tent door opened. Since the door face is angled back, it is also handy for changing clothes while standing inside the tent. I do wish more flat, headspace was designed in though, and a side mesh pocket or two. The last night I added the rain fly, which was taut and guyed out easily and well. Though not usually needed for my 3-season use, I expect the door vestibule will be challengingly adequate.
So I gain one third floor area and lose 1 lb 2 oz relative to my minimalist Roadster. (With my plastic ground cloth, my actual pack weight was 2 lb 8 oz.) More floor area and less weight - kudos to Big Agnes for a fine, game-changing product!