The biggest limitation to my use of Google Calendar so far has been the lack of synchronization to my mobile phone (so I can ditch the Filofax). While it is still in its infancy, there is now the promise of a solution to this problem with the release of gcalsync. I managed to actually get it to upload an event from my phone to my online calendar, but none of the online events downloaded to the phone (what's up with that?). Also, I have to give the program permission about ten times during its sync to read and write data to/from the phone and use the network interface (despite setting 'Ask First Time Only' permissions from the program's Java settings). So like the warning label says, still not ready for prime time, but let's hope this (or a similar application) offers the two-way synchronization desperately needed for Google Calendar to succeed.