I have built multiple apps in Titanium, and I have never experienced anything even remotely "horribly slow". The performance penalty is very, very small - undetectable to the average user. I am not sure the apps you were building, but, you do have to use common sense: you can't expect to build a highly interactive game with lots of complex calculations and animations in a dynamic language without a noticeable performance penalty. For 90%+ of the apps out there though, there is no reason not to use something like Titanium if cross-platform is your priority.