the really, really urgent update needed is the ability to send mail from an IMAP e mail account that is not one of the regulars (like gmail, yahoo etc.).
I have an iCloud e mail account which is my primary one (I have been all Apple until getting a Windows Phone a couple of months ago which was my gateway drug and I just got a Surface).
Having set up all my accounts on the Surface I find I can't send mail (receiving is fine) from my iCloud e mail address. I've checked all the details of the account and made sure I got the port numbers right etc.
Having hunted around online it seems this is a 'known' issue for people using other e mail accounts. It's really poor that they would release a product to market with this basic functionality missing. If I want to send an e mail from my main address on my Surface I have to do it using webmail in the browser.
Sort it out Microsoft!