[h34t]

Totally agree.

Maybe it could be a greasemonkey-added "Send later..." button that you have to manually click on every time (to avoid thinking you sent an email, but it was actually put into a queue) along with an input box for delay-time.

When you click it, it could (1) add a unique identifier to the subject, (2) save the email in drafts, and (3) send a message to a server-side app (which knows your Gmail authentication info) with the ID of the message and the time it should be sent. Then at the appropriate time this app logs in, finds message by unique ID, gets rid of said ID, and sends the message.