Disney made massive cannon changes on Star Wars, which is one of the biggest retcons since DC New 52. Which means many old EU works will be non-canon.

Cons
Yuuzhan Vong War never happens
Races such as Zeltrons and Killiks may not be cannon
Characters like Mara Jade are no longer canon
Old Republic will not be canon.

Pro
Chewbaccas death no longer happens
We can forget about Legacy comics
Kyp Durron doesn't destroy planet.
Some of Karren Traviss works are no longer canon.