Getresponse has also had it for a while, would really be great to see smth similar in Marketo. http://blog.getresponse.com/time-travel-has-never-been-easier.html
Many of the platforms that offer send time optimization allow for this option as well, by allowing you to set a default send time for each record based on their location.
This is something we would use as well. Silverpop takes this even a step further and has send-time optimization that claims to figure out what the best time to send to each individual is, based on when they typically open emails.
It would be nice if this were dynamic so that users could be sent e-mails slightly before the times they most frequently open them. Putting you at the top of their inbox when they're most likely to be viewing it.
Any update on this? This was requested over 2 years ago and clearly has a lot of supporters. Seems pretty pointless to suggest ideas if they aren't even processed despite having a huge backing.