Biggest changes from the film series to TV series?

What do you think are some of the biggest changes from the film series to the TV series? I would say one of the biggest ones is the casting of Snape which still divides a lot of fans. I'm keen to see what the new guy brings to the role though.

I think it'll take some getting use to seeing different actors and actress' playing all the characters.

But I think we'll get to see more stuff from the books than what they were able to put into the movies.