Another upside of Titanium (I'm busy with an app using Titanium) is that it's open source. See something that's not implemented? Hack some Objective C (for the iPhone client) and build Titanium, done. So you're essentially free to do what you want.

However, what I've also noticed that is that doing an iPhone-only app in Titanium definitely didn't go faster than doing it in ObjC, I'd say about the same speed. But that's my experience, for the app I'm doing now.