BirdieSync cannot synchronize iPhone events, tasks and mails for several reasons.

Regarding events, the problem is that the technologies provided by Apple have severe limitations regarding the management of recurring events. Apple has been aware of the problem for a long time, but hasn't done anything to fix it. The synchronization of events is under study to see if some workaround could be found to this problem...

If the management of "Reminders" (tasks) is now available in iOS 5.0, Apple hasn't provided any technology to third-party developers to manage tasks. So it's not possible to synchronize them.

The situation is the same regarding mails.