Everything.
The 2017 edition takes time to adapt when you're so comfortable working with the 2005 standard. It's a complete reworking in the likes of 9001 from what I've read. 18 deficiencies came out of our 2-day renewal assessment to 2017. Even with 2 months to prepare it caught us by surprise. I was able to answer and fix all 18 in the 60 days but not without a lot of help from resources like Eurolab, this forum, other Cabs like ANAB, and some from ours, A2LA.