I ended up getting Fantastical for Mac with a bundle of other apps that I really wanted. I think it works well as a menubar widget to quickly see my calendar at a glance. Beyond that I don't much use it, and I probably wouldn't pay for it on it's own.
Even though I probably wouldn't use this particular app, I really wish Apple would make stock apps replaceable with a new API to handle mail, calendars, maps, etc. The biggest problem is 3rd party apps, the general iOS and Siri don't hook into these 3rd party apps. If there was some software layer in-between that Apple developed to handle sending them to the right location then that would be great. When you launch an app for the first time, it could ask you if you want to use it instead of the stock app. As long as it doesn't keep asking, it could be handled like location services in settings letting you manage everything from one location.
Kinda off-topic: I wish if I refused location services for a certain website, it wouldn't be allowed to keep asking me on subsequent visits. Or at least time out after a month! I don't like giving Google my GPS coordinates when I browse Google News. They creep me out.