Frankly its usable, you have to work on it a bit. In the begning I had to export all the calender item to google then i deleted all calender from n900. Synchronised it and got half of the calender item to the device. then i imported the calender to mobile. this way i got some duplicate events. i deleted duplicates one and syncronised. so got same events in device and google.

Now the issue with sync If i put a new event in google it sync with device but if a put a new event in device it doesnt sync with google. I think the problem is mainly with the events repitition and alarm which doent let it sync. For me this is not a prob as most of the time i enter the new events in google. I think hopefully this will be fixed in new updates.