I started with an early version of Titanium, made a lot of progress very quickly, but ended up hitting many bugs and performance and memory issues.<p>Each new version of Titanium made steady progress, but didn't really make for a crisp, responsive app.<p>So I gave up, huddled down with a friend who knows PhoneGap, and rebuilt the app in PhoneGap.<p>Well, it turns out there are just as many stumbling blocks with PhoneGap as there are with Titanium - if you want a responsive, good looking app, you have to jump through many hoops. I was trading off one set of headaches for another.<p>I'm now back on Titanium. I've reworked the app significantly and am finally getting to a happy place - it's responsive on both iOS and Android, and looks good. Still a lot of memory usage, but no crashes, so perhaps it's not an issue.<p>My take at the moment: PhoneGap gets you more platforms and has a lower learning curve. However, it's hard (but possible) to make a native looking/feeling app. Titanium is a pain and requires a lot of discipline in your Javascript coding style, but you can get a nice native looking/feeling app if you're willing to put in the time.