Matt Cutts has this recent post on his blog about the one feature he really craves to have on Gmail – to be able to set timers to your mails to have them sent later or just delay them like the comments on digg are waitlisted for editing ( to avoid sending those silly typos).
A feature that I would really like is to set priorities on mails so they kind of float to the top or could give a little buzz after a while. I know the star feature and labels also could be great for that but still the list just grows. Also, would like to see some kind of activity from my mails.
Often, I have to refer more than one mail and in the huge conversation list that files up and its pretty hard making out one mail from the other in the line. Perhaps a new UI for the filing of conversations as well.
What more features would you want in Gmail? Or, if you do know about GreaseMonkey APIs that do nifty things, would be great to know about that.