Google on Monday formally announced full support for the CalDAV protocol along with the release of a small piece of software for Mac computers that lets users easily link up their Google Calendars with the iCal application.
Google had previously launched CalDAV support back in late July, however, consumers had to manually add their calendars directly to CalDAV-supporting applications like Mozilla Sunbird and Apple's iCal. The new Mac utility, named "Calaboration" simply lets users plug in their Google Calendar username and password to send Google calendars over to iCal. The benefit of doing this is the two-way sync. This means whatever changes you make on either end will be synced up to both every few minutes.
I gave Calaboration a spin this morning, and after restarting iCal, it worked without problems. With the current implementation you're able to see other people's schedules, as well as reply yes, no, or maybe to calendar invitations. The only problems I ran into early on were syncing errors where iCal would not let me write data to Google's servers, which was remedied with a closing and reopening of the program after the initial CalDAV setup.