Synchronizing your calendar between devices is still a mess. My personal calendar is on one account, my work calendar is shared with my personal account, and my girlfriend shares her calender with me as well. Initially I tried NuevaSync's Microsoft Exchange server to have over-the-air synchronization, and that worked well, allowing me to create events and have them appear, right away, on the Google Calendar account without intervention from iCal. The downside of NuevaSync was that every calendar event appeared as if it were on one calendar, so I couldn't tell which was work, which was her event (imagine everybody's surprise if I were to show up to an appointment she had with a heath care professional!), and which was a personal life event.
Google had CalDAV integration in beta, and recently launched it as an official service. That worked to keep iCal on my Mac synchronized well, but I could not add events from my iPhone. Having to move events over after a sync is not a habit I'm willing to form.
Spanning Sync is the least worst option, an endorsement that probably won't appear on their site. Through Spanning Sync, I get all my events in neat calendars but still have to manually synchronize the iPhone with the computer. It's something I have to do periodically anyway, so no loss there. The holy grail, of course, is direct, instant iPhone-to-Google Calendar synchronization.
Boris schooled me to Spanning Sync's referral program, which means that when anybody clicks through his image link, he gets a cool $5 sent to his PayPal account. Anybody clicking through that image also gets a cool $5 off the product. So in the spirit of trying to get something for free in an honest way, I encourage those frustrated with the state of calendar synchronization to click the image at the very top here to get me a fin, the term for a 5-dollar bill I learned from watching The Simpsons.