“I notice that you use plain, simple language, short words and brief sentences. That is the way to write English – it is the modern way and the best way. Stick to it; don’t let fluff and flowers and verbosity creep in.” – Mark Twain
This is an interesting one, and a challenge to balance, considering many writers have had success with fluff, but being clear, consice and getting to the point is usually the best route. Using too many “large” words can bore readers and distract them from the point of the story.
Another thing to consider, is filler. While writing my book, I find that I liked to write about a lot of different events between the plot events. The problem isn’t writing it, the problem is making the desicion to cut it. Maybe with the advent of ebooks, authors can give readers an option to read short or long versions.