Just finished the first episode. Screenplay was all over the place, really confusing, even for me, that had read the books. Some of the costumes looked not in place or cheap. But they've put A LOT of effort in the battle scenes, especially that last Butcher of Blaviken sequence was a piece of art - beautifully shot and executed (Guy Ritchie much). Loved it.
Now the acting, I couldn't tell much out of the first episode, but as I've pointed before - screenplay was all over the place and the fact that the series started in the middle of nowhere was really confusing and helping, but I thought HC was great - he had nailed Geralt' posture from the games to perfection, even the smallest things in the background. Calanthe was OK, I guess, Ciri's screaming was a bit too much, though. Looked out of place. To draw a better conclusion, I'll have to watch the rest of the season.
So, again - screenplay was a drawback, acting was up and down, mostly OK, though, some of the costumes are definitely questionable (and I am not even speaking of the NG ballsack armor), music was... trying, but seemed as a cheaper copy from the games.
I'd say the first episode was above average (6, maybe 7 out of 10 if I want to be generous, though it will be pushing, as 7 is actually a high score, but that Geralt sequence at the end was sick).