Personally, I really liked the first 3.5 episodes, but the rest (apart from the final 20 minutes) was not as strong and to be honest, for me, it was the same with the book. I just enjoy the devious angel/demon storyline more than the kids' adventure. However, I thought the children actors did an amazing job.
Overall, the casting for this was really on point. Michael Sheen and Dave Tennant were fantastic and the show was the strongest when the story focussed on them (episode 1 & 3 were the best). I also thought the styling was well done overall, especially for Crowley.
All the fuss about the Cumberbatch playing Satan, in retrospect, was as riddiculous as the reappearance of the Hammaconda in the jogging scene. They had Andy Hamilton (who did a radio show about satan) narrate the toad at the trial, which was a nice touch. And I agree with you @kieyra - I didn't like Frances McDormand’s narration either.
Such a pity that Christopher Lee isn't around anymore to lend Death his epic voice.
Adria Arjona and Jack Whitehall were pretty cute, and what a shame that we didn't get more of them at the beginning of the story. They are the sort of rich characters that Pratchett was known for and that could easily star in a story of their own.