I grew up with Star Wars (hell, my room is still star wars themed from when I was little), my experience is mostly with the movies and the Old Republic. Old Republic being my favourite time era in the star wars universe.

I got 3 books in with the skywalker twins, and about a book in with Admiral Thrawn so I'm familiar with them but not an expert.
So losing them as EU? I can't really say for sure, from what I read of Thrawn he was awesome and I think the movies owe it put him in the movies.
The twin's I'm more neutral on, I enjoyed reading about them (I only really stopped cause no book store ever had the next copy available) but I did read up online on the Yuuzhan Vong and it does get pretty over powered... Just like the clone war animated series, it might be wise to do something else with it.

But there's no reason to touch the Old Republic. That shit is far better written than the movies thanks to Bioware. They executed that time era so well that when I beat Revan in the sith flashpoint on the MMO I felt like I [b][i][u]killed my childhood.[/u][/b][/i] I have never had another game do that to me.