(Spoilers All) What are the best/worst changes made from the books to the show?

In your opinion, what deviations from the books made the show better, and which deviations made it worse?

For example, it always bothered me that the show completely abandoned the Targ's purple eyes. It would be simple enough to pull off, and I think it has/will become important when more possible heirs pop up. However, I think Daario's character was improved by ditching his bizzare look.

Changes could include changes in appearance, personality, story arc, location, etc.