iOS: Google released its Google Calendar app for iPhone today. Like the Android version, you have quick access to Gmail events, easy event creation, and multiple views to check out your schedule.
As far as functionality is concerned, Google Calendar for iPhone does everything you'd expect. Any events from your Gmail account are automatically added to your calendar, including flight, hotel, concert and dinner reservations. It will also suggest different events, places and people based on your history.
It also features a couple of different views so you can glance over your upcoming schedule quickly. Even better, Google Calendar works with the calendars already on your phone, including Exchange and iCloud. The app's available in the iTunes App Store right now.