I paid for the premium account, and it still is not letting me export into Outlook.
in order to integrate Todoist with Outlook, please download our Outlook plugin from this location: http://todoist.com/outlook and take a look at the video explaining its features.
if you want to use the iCal feed to add your tasks to Outlook's Calendar, please try to click on the calendar icon at the bottom of Todoist's Preferences -> General Settings.
By default, it should let you choose the application to open it with. If it doesn't, please go to the Calendar Tab in Outlook, right-click on Other calendars, choose Add calendar -> From Internet and paste the iCal feed URL.