Can't create repeating task that have to be repeated every first workday of a month.
When entered "first workday of every month" invalid date error occurred.
Unfortunately, such option is not available now, but we'll consider adding such syntax in future updates and you're welcome to vote for this request in our Votebox: http://todoist.com/Vote/show/6148/
I also really need this capability -- to be able to schedule in advance a task that will repeat. So say today is Aug 15, I need to schedule a task for Sept 1 and the first of every month thereafter.