Does Plaxo for Mac provide iCal support?
Yes. Each of your iCal calendars will synchronize to a matching calendar folder in your Plaxo online account. Click here to get started.

Will Plaxo support synchronization with Notes and Tasks in my Mac Address Book similar to Plaxo for Windows?
Currently, Plaxo for Mac will only synchronize contacts and iCal events. Future versions of Plaxo for Mac may include synchronization capabilities for other data types.