Two things I would love to see in Outlook, now that I'm using it all the time:
1) Aliases should be able to used from more than just outlook.com. Using the mail app on Windows 8 or Windows Phone 8 I am not able to send from my aliases, even if replying to an email that was sent to one. Apparently now they have the ability to specify an alias that you can use as the default for all devices, including mobile... but then I can't reply using my primary.
2) Allow more than one criteria in the "rules" (filters)! My dad forwards chain mail jokes and such to me all the time, and I have a filter set up to catch anything that says FWD: in the title (and another filter to catch FW
and place it in a folder for later perusing, so I can avoid stuff like that for months at a time. Since I can only specify that ONE thing, any email I forward to myself or someone else forwards to me ALSO ends up in that folder (this includes forwarding of flight itineraries and such), so I have to manually search it myself from time to time. On my Windows Phone, I don't see any messages that go into this folder at all... and I refuse to choose to sync that folder because then I'll start getting alerts for messages in that folder! No thank you. So I'm forced to manually check this folder at outlook.com every so often.