I will use the OWA version when I need to do more detailed Outlook responses to emails or events. But I do use my RT tablet as a mobile device, looking at emails and calendar between meetings and such and thumbing through while holding the device and walking or standing. And I do look at the live tiles for information and with 8.1 and larger tile ability, there will be even more information available to look at. But tasks are still missing an app and there is just no reason for that. None. A web app is not going to replace that omission.