My Big Agnes Fly Creek UL3 arrived today so I've got some initial weight & measurement specs.
WEIGHT
Excluding a few rubber bands and disposable plastic bags, the complete package tips the scales at 3.67 lbs. This breaks down as follows:
Fly: 477.1g or 16.85oz
Body: 549.8g or 19.42oz
Poles: 440.7g or 15.57oz
Pole Bag: 11.3g or 0.40oz
Stakes: 13 @ 11.1g = 144.3g or 5.1oz
Pole Repair Tube: 11.3g or 0.40oz
Stake Bag: 5.5g or 0.19oz
Tent Bag: 23.4g or 0.83oz
To properly stake down the tent is appears that you need 8 stakes including 4 for the corners, 2 for the vestibule and 2 more for the sides of the fly otherwise they'll be wacking the inner tent. So a reasonable 'trail weight' with 8 stakes and no pole bag or repair tube is 3.50 lbs. The minimum weight (fly, body & poles) is 3.24 lbs…actually it's 3.20 lbs if you don't count the pre-attached guyline on the fly like the mathematicians at Big Agnes. These numbers are very close to Big Agnes claims which is very good.
For me, I will be using this tent with lighter 8g stakes, Zpacks cuben stake bag and lighter guyline. The fly comes with 17.8g (0.63oz) worth of guylines pre-attached. Replacing this with spectra cord should cut this at least in half. I also snipped a couple tags off. My estimate is that I will be able to hit the trail at 3.37-3.40 lbs.
DIMENSIONS
Big Agnes claims a 90" floor length with a width of 66" (door) tapering to 60" (foot end) and a height of 42". I found the floor dimensions to be significantly smaller than this, but it's hard to really give accurate numbers without the tent corners staked out, as that would pull the floor a bit larger. I measured a floor length to be a largely usable 84", as the door and foot end walls are quite steep. I measured the width at 62" (door) tapering to ~55" (middle and foot end). I think with the corners staked out you might gain an inch or two of width at the middle of the sides. In any case, it's tiny for 3 people but quite spacious for two.
Here is the tent shown with two regular size pads. The pads are pushed to the outer sides of the tent so you can see how much extra width remains between the pads. One pad is slid to the back of the tent, while the other is up against the door:

On the positive side, I found the height of the tent to meet or slightly exceed the 42" claim. I measured just under 43". The headroom is excellent in this tent, with the roof being quite high over a very large portion of the tent.

COMMENTS
The fabric used for the fly of the tent is really nice stuff. It's super light nylon…possibly 10D but I'm just speculating. It's definitely lighter than 30D.
Aside from clipping tags, using lighter stuff sacks and stakes, and replacing the guylines, the only way you could save a significant amount of weight would be to replace the pole set with carbon poles. It would be hard to do because of the hubs, but a theoretical carbon poleset could probably weigh in at 250-300g compared to 440g. The tent body and tent fly are made of such light nylon that even cuben would only save a couple ounces.
As known, the door of the tent is susceptible to rain falling in when the fly is open, but the door is closer to vertical than expected, so this is a smaller issue than thought:

Big Agnes claims 4 mesh pockets, but there are actually six. There are two on either side of the door at the bottom, and then one more on each side at the top:

LIKES
– Use of very lightweight/low denier nylon
– Tons of headroom
– Overall a ton of space for the weight
– Fully freestanding
– Double wall
– Use of fabric (instead of netting) on the lower walls
–
DISLIKES
– 1200mm floor rating
– Door susceptible to falling rain
– Inner needs to be set up first
– No vents
SUGGESTIONS
1) Up the waterproof rating of the floor by applying more/better PU coating to the same lightweight nylon. 5-10K mm rating would be nice.
2) Use a waterproof/uretek zipper on the door. This would save the weight of the fabric flap and the velcro and it would be simpler to use.
3) The floor size is great for two, but if Big Agnes actually wants to sell it as a 3 person tent, the floor width shouldn't dip below 60".
4) Make an Easton airlock carbon fiber poleset available to chop off 6-8oz.
5) Make the door vertical, so falling rain usually won't enter.
