I use Jim Dunlops, I don't remember what mm I use on my acoustic, but I know that the thinner the better for me for the same reason as PRSplaya. Thick picks on acoustics just sounds too clunky for me. On an electric though, I use a .88mm. I find that I have more control with it since I typically play faster on the electric than I do on the acoustic. Tis one of those things that we all must discover for ourselves.