It's... not great.
If you are a fan of the games or the books I expect you'll be very happy, but otherwise it just feels like there is nothing much to it. Script is pretty bad, acting is fine for the main characters, but terrible for others, plot is both generic and confusing at the same time.
It looks great, Cavill does a great Witcher, but unfortunately his performance is a perfect video game adaptation of the Witcher, which doesn't mean its a good thing to do to make a great TV show.
I've done 3 episodes, and the third episode was actually quite enjoyable, despite all that. I expect I'll finish the series.