How to seamlessly sync contacts and calendars across devices? I currently have all my contacts and calendars on my Mac, but would like to sync them over the air with my other devices (iPod, iPad and Android phone). I also want it to be multidirectional: being able to add, edit or delete from all devices. 

As far as I understood from reading other threads, the best bet is to keep all calendars and contacts on Google and sync them with the other devices. This means not using iCloud to sync calendars or contacts.

Is this correct? Do I really have to move all my contacts and calendars to Google Contacts and Google Calendar in order to have them synced across all devices? Will I be able to add contacts or edit calendars from any device and have them in sync as well?
Yes, the best way to sync cross platform is via google.

By far the easiest most care free way to sync all contacts, calendars, email etc is to have all Apple devices, this is how Apple meant for this service to be used.

Google has done a good job of making this service available to people working on multiple platforms.