write slow or write fast?

I've been reading an interesting book lately The Writing Workshop Note Book by Alan Ziegler, who's on the faculty of Columbia University's Creative Writing program. The book includes quotes and information on creating, writing, language, revising, workshopping, editing and more. One discussion that caught my attention was about the speed of writing. At one point Ziegler says

It takes skill to work slowly. When I was in graduate school, a classmate complained, "I wrote for five hours today and only got one paragraph."

I replied: "I'm not a good enough writer yet to do that."
Clearly there are two different approaches to writing: slow or fast.

For example, here are some more quotes related to writing:

• If my doctor told me I had only six minutes to live, I wouldn't brood. I'd type a little faster. --Isaac Asimov
  
• Write your first draft with your heart. Re-write with your head.--the movie Finding Forrester
  
• Don't get it right, just get it written.--James Thurber
  

Personally, I think there's something to be said for getting the first draft finished without getting bogged down by your internal editor/nay-sayer.

So, how about you? Do you write slow or write fast?