If I remember correctly, you ate at Cosme a year or two ago, no? It has improved markedly since then, though I'm certain it's still not on Pujol's level.
As somebody who has dined at Cosme twice within the last month, for dinner and brunch, here's my take. The large-format dishes, both the duck carnitas (dinner) and lamb barbacoa (brunch) are exemplary. Cosme sources their corn from the heritage growers in Mexico, so the accompanying tortillas are fantastic...only ones that compare that I've had in LA are at Taco Maria.
The corn husk meringue will very quickly be one of the best desserts in our entire city.
Other dishes are much more hit and miss. Cobia al pastor was a fantastic take in my opinion, much better than the fish al pastors that Salgado puts on the menu at TM. The uni tostada is fine, though the uni sourcing varies more than one would like.
At Cosme, when dishes tend to fail, it is because the dishes use very little spice, perhaps to appease the NYC clientele? At Taco Maria and Broken Spanish (the soCal temples of alta mexican) Salgado and Garcia will serve things spicy if they want it to be spicy. I remember a quote from Salgado essential saying he wanted his aguachile to be too spicy for half the population. Cosme is the exact opposite, and some dishes fall flat because of that. A NY strip tartare served with smoked beans and habanero will be shockingly lacking in habanero, rendering the dish a bit too single note. Same thing with the tyaluda.
Another thing about Cosme. The best way to enjoy Cosme is to go all out. And that gets absurdly expensive. On my last dinner here with the significant other, I spent 250 dollars and I think only 45 of that was drinks. They sell Dos Equis for 14 dollars, micheladas for like 16. That's exploitative. Hopefully LA rent will mean things are a bit cheaper.
But overall, this will be a really nice addition to the LA dining scene.