[Ken Case]

Is this when you first log into Lion? I've noticed that everything can be slow when I first log in: Lion presents a picture of what you were doing when you logged out, then slowly substitutes all the fake windows with real windows as it works through resuming all the apps and context that were there before. (You can see this happen in Terminal if you have windows open: the former text dims once the windows actually become live.)

So if you're seeing this when you first log in and resume your entire Lion session, I guess I'm not too surprised by a 15-20 second delay. But if you're seeing this at other times, it doesn't sound normal to me (since you note that subsequent launch times for you are nearly instant).

The next time this happens, could you pull up Activity Monitor, select OmniFocus (it might help to use the Filter in the toolbar), then press the Sample Process button in the toolbar? That will tell us what OmniFocus is doing during that delay: whether it's working on some internal database upkeep, or waiting for some external service, or doing something else altogether.