I have not played the game or read the book, so this is my personal opinion in regards to just the TV show itself.

1. The teaser added nothing to the story, I don't know why it was even there, I thought it was ridiculous. 2. Dialogue was a bit on the nose, I thought the exposition was pretty bad as well. 3. In addition to the dialogue, it seems the writers did not get any consultant on middle age english, because the way how the people speak in the witcher, does not sound very medieval at all. I mean seriously, one guy said to his girlfriend, the reason he did not give her roses because it was to cliche. SERIOUSLY, you used the word cliche for a MEDIEVAL drama, do you know the word cliche has only been around since the middle of the 20th century. I just think the writers need lessons in the middle aged english language. Because they speak like modern people. 4. Some of the acting was pretty bad although some other actors was very good. 5. The fighting looked very bad, how many times is someone going to spin in a sword fight? Seriously? You are fighting someone with a sword and you keep spinning around like a dancer, ridiculous in my eyes. 6. The armour was very bad, looked really horrible.

Overall I am not invested in the story, I just don't think these guys thought this through properly. Most people who are giving this 10/10 are fans from the game it seems, but take away the game and judge this as a TV show by itself, it is not that great.