I think you have to offer some more steps of increase in text size for comfortable use on large screens with high resolution, such as the Imac 27. Right now it is comfortable to use this great program on laptops or desktop computers with smaller screens. In iMac 27" it is possible to use Agenda, but it could greatly improve the user experience just one o two more steps of text increase.
You could also enlarge the icon that allows collapse or uncollapse the items.
Thank you very much and Congratulations.