Just found this thread while poking around for info on the T3 (and T4) related to a problem I've had. I have owned the T3 for about a month now and have taken it on three trips. Overall I really like it - its perfect for me and the dog, but as mentioned previously, a cot won't fit along the sidewall without contacting the corners. It's do-able with two people & cots, but very tight (the T4 is probably a better choice if you want to sleep on cots). For me and the dog, I can put gear along one wall and put the cot more toward the center and still have plenty of room for the dog.
Setup is not quite as easy as you see on Youtube (at least not for me). It is much easier with two people so that people can pull against each other on opposite sides. Otherwise it takes a bit of fighting with it to "pop" the sides out and get them to stay. I have found that leaving the fly in place greatly stresses it when collapsed (and won't fit well into the zippered bag) so I remove the fly when packing it away.
The bag is really nice - not waterproof (because of the zipper) but the construction quality is excellent, with padding on one end to protect the tips of the poles that jut out when the tent is collapsed. There are high quality grab handles at both ends that come in super handy, as well as a very night shoulder strap that is well padded.
The problem I've had is that after my very first trip, I came home and set it up to clean it out and found that there was a roughly square pattern of wear in the very center of the floor. After my second trip, this wear actually caused small holes through the bottom requiring a patch job with some Gorilla tape. It appears that while folded and stowed on my roof racks, the inside poles are somehow rubbing against the floor material after just a few hours of riding on the roof racks and causing holes.
The other issue I have found with the tent is that anywhere a run of stitching has started or stopped, there is about a 0.5mm pinhole that goes all the way through the tent fabric. I noticed this my first morning waking up in the tent as the sun came up, I saw light streaming in through these pin holes. Mostly they are around the reinforcement "pads" at the center of each wall panel where the poles come together to form the "hub" that you pull on to set the tent up. I've been in some light rain and not had a problem, but I could see these holes weeping in a heavy rain, particularly if there is wind.
Overall, for the price I paid (under $200 delivered) I have to say it is one of the easiest to set up and most comfortable tents I've ever owned. The design is very good, and there are a lot of thoughtful features such as interior mesh storage pockets and a removable floor. The standing height is a wonderful bonus, especially for someone like me who has owned and camped in nothing but backpacking tents & tarps my entire life (over 40 years of solo camping!)