My company uses Google Calendars to track each others appointments, so to sync with iCal (and my Palm) I need a Google Calendar sync. Tried all the Mac solutions I could find:

-gSync - Unusable. Duplicates calendars,many other issues...
-Plaxo - "free" but can only sync your calendar, not the ones you subscribe to, so useless for me
-Spanning Sync - works, but limited in scope. Also not crazy about going through their server...

This one works the best of the lot. There are some quirks, mainly in understanding iCal (like NEVER have a duplicate event at the same time, iCal freaks over this when you Sync through .Mac sync... So if you have 2 calendars that have a common event like a conference call, be careful that both don't show up on your calendar) I really like that this not only allows my Google calendar sync, but allows me to sync multiple Macs.