So, what do you guys think of Sunrise Calendar?
After using it for a day, it seems pretty great. I'm not quite sure what makes it so "smart" (which is how it's advertised), but it's definitely well-designed, it does a good job of integrating and displaying lots of information collected from multiple sources, and it feels at home on Android. It has an attractive widget - not quite as nice as Today Calendar, but way better than the stock Calendar. In general, I would say it's a huge improvement over the stock Google Calendar app in almost every respect.
The only thing that freaks me out a bit is that the app is completely free, with no paid version, no ads, no IAPs, and no subscription service. It kind of makes you wonder what their business model is. I assume they're planning to use a model similar to what Evernote, Dropbox and now Pocket are using - build up a lot of users by offering a high-quality service for free, and then try to convert some of those users to paid subscribers later on by offering a "premium" version. We'll just have to wait and see.