[update: Google now has an app that'll setup the gCal / iCal sync for you. Sweetness. link]  

So first, let me lay down the framework of what I’m trying to accomplish. At work I’m now using google apps (gmail for domains) instead of exchange server. But I’m so used to the Outlook interface that I set up Outlook as an imap client for gmail (don’t forget to enable imap support in the gmail interface). So where does that leave me for a calender? Well luckily google already has a windows desktop app, google calendar sync, that sync’s gcal into the outlook calendar; so I’m covered there.

But at home, I’m primarily on the mac which means I’m using iCal and then syncing that to my iPhone. Google calendar has CalDAV support. Just follow the instructions and gCal and iCal sync. Which also means that if you set your iPhone to sync all calendars you’ve now got your gCal on your iPhone.

None of this was more than a google search away so the reason I’m recording this is to remind myself of one small, undocumented step. Either that or I just don’t know how to use iCal … which could be the case.
Appointments created on other calendars in iCal don’t sync to gCal.
That means any appts on your Home/Work calendar don’t make it to gCal. I kept banging my head against the wall trying to figure out why they weren’t working. Sounds obvious now right? Not so much at 11pm last night.

What you have to do is select the gCal calendar in iCal and create the appt there for it to sync. Duh. Not the most intuitive though. And if you put your personal appts on your home calendar they’re not going to be marked as busy for your gCal (in my case work) which could cause scheduling problems.