I like using the built-in iOS Mail and Calendar apps for my Google accounts. I can't delete 'em, so I might as well use them. Otherwise my OCD will take over, and in general they seem to work just fine for me and my weird workflows...
.. Except for one thing: They only show my primary calendar. I have access to a handful of shared calendars and there's no easy way to display them.
Turns out that there's an option to display more calendars. Go to the Google Mobile Sync page from your phone, find your device, and check off which calendars you want to sync. Then blammo, the Calendar app will allow you to enable/disable syncing any or all of them. How convenient.
(And yes I see the "Sync with your Mobile Device" option in Google Calendar, but the diddler to set up multiple calendars took me through a whole bunch of FAQs. It's kind of buried in there.)