When I get a new e-mail from my gmail account, and I open the message directly from the notification panel, the notification icon persists. I have to press 'back' to go back to my inbox after reading the message for the icon to go away. I can't just press 'home' - the icon will remain if I do that. Or I can clear the notification manually with the 'clear' button, of course. I assume this is not a glitch - this is the case with everyone's? Do you find this annoying at all?
I don't have the same problem with my corporate e-mail account, since the notification takes me to my inbox, instead of the message itself. The icon goes away as soon as the inbox is opened up.