Hot on the heels of the new version of Gmail Mobile for the iPhone comes a new mobile version of Google Calendar leveraging some of the same technology. The previous iteration was frustratingly feature-poor, allowing you only to view your appointments and add new ones using a natural language interface which could be frustrating with the iPhone's keyboard. Thankfully the new version has a more typical appointment entry screen.
Better appointment entry is nice, but the big new features in the new version of Google Calendar for the iPhone are the ability to edit existing appointments, invite other people to events, and the ability to manage appointment invitations and attendance statuses.
Although the official announcement on the Official Google Mobile Blog inexplicably downplays it, Google Calendar now has a modicum of offline functionality on the iPhone and Android phones. Now even if you have no network connection it can still show you appointments that you've previously viewed, though you can't edit them. Hopefully this matures into a true offline capability in future versions, but it's sure nice to know that you can get to your appointments if you need to when you're without a network connection.