I also finished the game. I started off really positive that would concur with the hype, but by the end I could only really enjoy the narrative. Gameplay--way too easy. I admit, I'm a card game vet and even familiar with Gwent, but there seemed to be very little thought put into battles after the first couple of chapters. I had to change my deck for only two boss fights (Gernichora and aep Dahy) out of the hundred or so battles, fifty of which are the exact same, monotonous random Nifgaard spam. Decision/rewards are too binary, unlike the best of The Banner Saga/standard-bearing CRPGs. There's very little (gameplay) incentive to do anything but the most obvious, best choice, bar maybe two exceptions. Puzzles also stopped being puzzles with interesting solutions and either become a) free-for-all fuckfests of just doing stuff until one of ten/twenty solutions happened, or b) weird programming experiments that tried to make other games (Hearthstone, Bejeweled, escape-the-tower) work on the Gwent engine. All of which seems to confirm--if you played Gwent, at least--that CDPR might not be the best at balancing/designing this kind of game.
It reminds me very much of Ni no Kuni II in that regard, in that on the surface and at first impression, it's very good, but playing more it slowly becomes less than great.
Also, there's a bunch of bugs, some of which should have never made it through basic playtesting. Strays of Spalla has an effect which seeks out a row with "Fire", and it doesn't work if the row has... "Fire+". Quite a few effects simply stop working if you mulligan them away. A bunch of flags aren't correctly set in game files when you make decisions meaning they have no impact at all. And the one pretty much everyone is puzzled about: there's 4 golden chests on the final map needed for an achievement that are simply not placed at all.
Play it if you want additional Witcher lore, I guess. But it stopped being whole-hearted fun and strategic a few hours in.
Gameplay tips: pretty much every card is broken. Literally all of them. Almost every single Gold or character card is insane at various points you get them. Caldwell will carry you through Act 1. Rayla + Xavier (+ Reynard + Knickers) ends up pulling 7 cards out of your deck with only one card in hand, although maybe that's supposed to be balanced by Rayla being fairly easy to dismiss? Eyck does crazy things against monsters, every artifact is just about broken though I used the Manticore trophy for 98% of the game, Gascon+ and Isbel eventually become crazy as well. Bombers are 8 point bronzes with effectively unnerfed gold weather (i.e. 20-60 pts) and Slingers are base 20. Eventually you get access to units that just start on the battlefield (free cards and optional thinning?) and thinning options that just pull out 5 cards from your deck and give you 50-70 points worth for 2 cards in the process, so there's very little thinking involved. You'd have to purposely build a deck with the goal of having it be not absurd, and there'd only be like 5 or so options to choose from.