announced this afternoon a new feature called Background Send, which will...wait for it...send emails in the background of your webmail experience. If you turn the Labs setting on and select the new feature, your interface won't hang while it sends one email before you can send the next. You can just sit there and crank out emails like you were Tweeting tweets or sending Instant Messages. Initial tests do not indicate any increase in speed of responses or any additional hours in the day to respond to emails.The Gmail Labs team
To be honest, I can't tell the difference yet - but I hope I will be able to in the future. The old days of slow computing are past us now - elegant and memory managed technical (if not mental) multi-tasking is a big frontier for the future. Check out Background Send and tell us if you can tell the difference yet.
Joel Falconer at The Next Web says about the new feature that it would be even more valuable if it allowed email attachments to be uploaded in the background after hitting send. Good thinking, Joel.