Other than receiving an email of my daily agenda from the Sunrise calendar, I can't think of another calendar program (the default iOS app included) that sends you email summaries, and I think they're a great addition.
The interface implements the flat design in line with iOS 7 and feels like it belongs on your iPhone. Switching between different views and general navigation of the app was fluid. Scrolling through a never-ending list of dates didn't lag, and transitions between screens and menus happened smoothly.
Going beyond the basics
Tempo nails the basic features I expect to find in a modern calendar app. The recent update enabled natural language input (i.e. "Lunch with John on Tuesday"), incorporated iCloud Reminders directly into your agenda, search, weather forecast for current and upcoming days, and multiple views.
In addition to the staples I just mentioned, Tempo's unique feature set is one that expands upon the contact updates I mentioned earlier. By connecting an email account to the app, you're able to view any email exchanges it determines are related to your upcoming appointment with a tap of a button.
I let Tempo scan my email account for messages related to a doctor's appointment knowing there were no messages available. At the conclusion of the search, Tempo found several emails, but none of them were remotely relevant to my appointment and so it didn't display them. A second search for an event that originated from an e-mail conversation was properly surfaced.
The overall experience of Tempo is a pleasant one. The basic features are included and work as they should.
Where Tempo excels past its competition is by surfacing relevant information for contacts and appointments. By keeping tabs on your contacts, making it easy to recall an important email or provide directions to your appointment, Tempo wants to be your go-to scheduling app. Unfortunately, Tempo's capabilities are available on just one device right now, and that's disappointing.