Titanium is a mixed bag. For simple applications, it's great, but as soon as you need to do something a little bit complicated, the learning curve goes up quite a bit.

For example, in my app (http://iphone.albumpl.us) I had to write a couple of small custom objective-c modules to get some camera/image stuff to have sufficient performance. But overall being able to write most of it in CoffeeScript, is so much better (enjoyment-wise and speed-wise) than having to write everything in objective-c.