Before I start, I want to say I like the EU. Without it, I would enjoy Star Wars as I did. But there are things that do irk me at time. I can't I hate some things as I haven't looked at a lot of EU material, but there are things I can say that I dislike:
- Repeating Anakin's fall with Jacen.
- Repeating the Jedi Purge with Krayt's Empire.
- Turning A'Sharad Hett, a Tusken Jedi, into a Sith Lord.
- Making the EU from NJO and onward a little too dark.
- Bringing the emperor back from the dead (which is probably the #1 argument why the EU shouldn't matter).
- The constant retcons (Moraband?).
- The Force Unleashed
- A little too much Jedi vs Sith
- The weird stuff happening in the Dawn of the Jedi comics (lightsabers during the founding of the Jedi?)
However, there is one thing that I absolutely hate:
SWTOR: REVAN!
I grew up watching my brothers play KotOR 1 and 2 and I loved seeing the stories of Revan and the Exile in these games... Sad to see that they're thrown away in one book. Heck, I'm doing a better version than this!
... but that's just me.