I am using OmniFocus on Mac, iPhone and iPad. It is syncing via WebDAV to five devices (three Macs, one iPhone and one iPad) and I am extremely happy with the syncing performance. Fortunately, my organization provides a WebDAV space.

I use OF for Mac to process my inboxes. Most of my input comes from email (Mail.app). I use the OF clipping shortcut to process email and the MsgFiler add-in to Mail to quickly organize (file). I have found it is well worth the effort to learn OF shortcuts and to customize the Perspectives.

OF for iPad has a very nice interface and I prefer to do my Weekly Review on it once I've cleared my inboxes. OF for iPhone is really just used for reading my lists on the go. I still prefer paper for capture.