The next update to Planner has a custom month view. It's the best way to see what's happening beyond the current week, of course.
The 1.1.0 update also has lots of fixes and lets you sync with the built-in Calendar app on the iPad. If your Calendar app is set up to sync with Google Calendar, MobileMe, or other calendars, you'll be able to see and edit those events from within Planner. The changes you make will be sync'd back to the calendar they originated from. It's optional - just flip the switch to turn it on or off.
Look for Planner 1.1 in the App Store soon.