From the support article, it appears (maybe) that the device registration model has changed as part of the push syncing. If so, does this break backwards compatibility with OF 1 (on OSX or iOS)?
As it stands, push-triggered syncing will not break backwards sync compatibility. The push notifications used to trigger a sync are an additional service provided alongside OmniFocus’s current sync system; when a push notification comes in, OmniFocus performs a sync just like it has for years. We’re simply using push notifications to cause these normal syncs to happen more frequently, so that changes get moved around faster.
It is worth noting, though, that while older versions of OmniFocus won’t be harmed by push-triggered sync, they won’t be helped, either: OmniFocus 1 doesn’t understand how to send or receive a push notification, so it will continue to sync exactly like it does now.
Thanks! Just wanted to know if updating iOS before OSX was possible (waiting for 2.3 to try it again).