The killer app for my user is push email which is simple to setup with the standard BB offering and an IMAP server. He can live without OTA calendar and contact syncing but he needed OTW syncing. We've achieved that.
In the reading I did about ical syncing OTA with the blackberry, I read that the latest version of the BB software (on device) supports ical invitations via email. I haven't tested it. We only have one blackberry and one crackberry addict. I used to have one but broke the habit.
Jason