tl;dr: No. You don't need a screen protector.
I have had my Captivate for over a year now. In that time, I have used neither a screen protector nor a case. It would often ride in my pocket with change and/or keys, or on my dashboard, where the "sticky pad" proved often not to be as sticky as advertised and would allow my phone to be thrown under the seat and into other parts of the car. In truth, I haven't been very kind to my Captivate, even getting mad enough to throw it once after a botched ROM upgrade. Suffice it to say, I have given the screen plenty of opportunities to get scratched.
Just now, I wiped my fingerprints off the screen, and took a picture of the screen in the least flattering light possible. As you can see, it looks like I did not do a good job of cleaning it, but it's obvious that there is not a single scratch on it, and certainly nothing that would affect the functionality of it. Even examining it with a magnifying glass and running my fingernail across it in all directions could not reveal single scratch or pit. The glass is still as flawless as the day I bought it.
Last edited by Archpope; 5th September 2011 at 08:38 AM.