Do it, lack of markdown is the one thing that has me ditching Evernote for a few years and then coming back for a little while to see if it's been added, and is the only thing stopping me and probably a lot of others from biting the bullet on a permanent subscription.
My main use case is for creating documents on the go from scratch notes, without then having to reformat it in the tools or platforms my client uses. Almost everything supports Markdown in some form.
My gut feel is that the omission is intentional to make it more difficult to leave Evernote, but in this instance it's stopping people from adopting it in the first place.
