Wirelessly posted (iPhone 3G (white): Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_0 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7A341 Safari/528.16)
Settings - Brightness
Actually, I've never seen my iPhone or either of my iPods (iPod touch 1G and 2G) auto-dim, only get brighter when necessary. Are you guys saying the 3GS actually auto-dims now, too?