Okay, A housemate took a look at it and figured it out:
func addCategory() {
var popoverContent = self.storyboard?.instantiateViewControllerWithIdentifier("NewCategory") as UIViewController
var nav = UINavigationController(rootViewController: popoverContent)
nav.modalPresentationStyle = UIModalPresentationStyle.Popover
var popover = nav.popoverPresentationController
popoverContent.preferredContentSize = CGSizeMake(500,600)
popover.delegate = self
popover.sourceView = self.view
popover.sourceRect = CGRectMake(100,100,0,0)
self.presentViewController(nav, animated: true, completion: nil)
}
That's the way.
You don't talk to the popover itself anymore, you talk to the view controller inside of it to set the content size, by calling the property preferredContentSize