Autorun in Win7 doesn't read the OPEN command from autorun.inf file (it only reads LABEL and ICON) that worms use to infect your USB. It only displays options to start applications you have installed on your PC. This is indeed safer, but I still find no use for the autorun feature so I disable it. Plus your USB might still get infected if you plug it in a Windows XP or Vista PC. This is why I use the USB drive vaccination (that simply creates a clean autorun.inf file that malware can't infect...hopefully) feature from Panda USB Vaccine. I think there is an update for Vista that disables autorun for USB as well.