I think that numbers 2 and 4 are pretty much a given. It's my understanding that "Fast App Switching" is pretty much an inherent result of updating the app to use the iPhone OS 4 SDK, and "Local Notifications" is something that Omni has been wishing they had for a very long time -- the kludgy subscribed-calendar workaround was specifically required because they couldn't get local notifications, and Omni has said numerous times on these forums that when and if a local notification service became available they'd use that instead.
"Task Completion" doesn't seem like too complicated an idea either, and would probably be a good fit for just about anybody.
While it seems like a cool idea on the surface, proximity reminders seem like they could be very complicated to implement properly in an app like OmniFocus...
- Firstly, what distance should you need to be within in order to trigger a proximity alarm? While I suppose it could be user-configurable, the vagaries of location services on the iPhone OS platform would mean that too small of a number may never trigger a proximity alert, and too large of a number may trigger false alerts.
- The problem may be exacerbated even further by the way OS 4 will handle background location -- it sounds like by default it will only re-check location when you actually change cell towers, which means that if you're walking around a neighbourhood it may never re-check to figure out that you've come in proximity of a target location.
- Alternatively, even if a full always-updating background location mode is available in the SDK, it would be hell on your battery life.
- Further, it may not work on non-iPhone devices like the iPod touch or iPad at all if it's tied to cellular tower monitoring.
IMHO, unreliable alerts would be worse than no alerts at all because you'd fall out of the habit of checking the app and instead rely on notifications that you might not receive consistently.
The fifth item isn't actually all that hard to accomplish right now using the subscribed calendar method, except that it doesn't happen natively on the device (it requires an Internet connection), and it's kind of an all-or-nothing deal rather than being project-specific. I could see the use for this feature for some users, but regardless, this is something that Omni could have easily implemented in the Mac version a long time ago and doesn't really require the new iPhone OS 4 features unless you're only using OF on the iPhone -- if OF on the Mac updated iCal on the Mac the information would sync up easily enough through the normal conduits.