Well, they can go back to the drawing board and do some more research. This was an example posted here a few weeks ago, by a heavy Calendar user. Look at the old and new app and see if you can answer a common question for a calendar user, like when do I have some free time in the next month: http://imgur.com/a/Qo91p

Also, not that it matters, but the old app is 2 MB and works flawlessly, the new one is more than 20 and chugs a bit when scrolling on a quad core processor.