I just installed the Tesmanian mats in my new Model Y. They arrived a week before the car did so they sat in their box for a while.
The two larger mats (rear footwells, trunk) were folded to fit in the box. Despite the instructions in the box saying to lay them flat for 24 hours before installation, I let them sit flat for about 10 minutes, saw no remaining folds or bends, and installed them immediately. The fit is pretty much perfect.
I had the first-generation Tesla branded mats (manufactured by MacNeil - Weathertech) in my Model S. Here is a comparison:
FIT: no comparison. The Tesla front mats were perfect, which is good as I don't need any tangling in the pedals TYVM. But the rear mats hung up on the seat wells and even the side trim at the edge of the carpet. The Tesla trunk mat was just off by about a half inch and developed a permanent crease. The Tesmanian mats all fit perfectly with no more than 1/8" gap anywhere and no folds or creases.
MATERIAL: The Tesla (Weathertech) mats are made of a somewhat more rubbery material and have a slightly grippier texture. I suspect I'll have to take a little care things don't slide around in the trunk with the Tesmanian mats in place. However, neither mats felt slippery underfoot, and I consider the Tesmanian material plenty good while the Tesla (Weathertech) material is... somewhat better.
PRICE: Obvious. The Tesmanian mats are about a third the price of the Tesla OEM mats (are these still made by MacNeil?), and also quite a bit cheaper than the Weathertech-branded mats.
DONATING YOUR MONEY TO DONALD TRUMP: MacNeil's a big Trump donor. If this is a plus for you, this is a reason to buy Weathertech or other MacNeil-manufactured products. If you can live without this, I believe Tesmanian is a superior choice all-around.