I bought my Nokia N97 early July, just a few days after the Australia release. I’ve been enjoying this great device since then desspite its bugs. The most notable of which was that unlike my previous Nokia S60 it would not cooperate with iSync. Thankfully the recently released firmware update (V20.0.019) fixes this problem.
After hacking the Nokia 5800 phoneplugin and turning off contact sync in iSync I got older firmware versions (V10, V11 and V12) to sync my calendars. This was the most important thing for me, but still very annoying.
First download Nokia-N97.phoneplugin.zip. Extract to ~/Library/PhonePlugins/ as usual. Now pair your phone with bluetooth and select the option to enable iSync. Open iSync and turn off contacts sync. It should now sync calendars properly. This is where I’d been up to V20.
To get contacts to sync you need to reset the contacts database. Insert a MicroSD card into your phone and do a backup of your contacts from the phone’s “File Mgr” app. Now immediately restore just the contacts, the phone will reboot. Turn on contacts sync in iSync and it should work great =)