I started using Appcelerator Titanium for a personal project. Here I am with my experience so far with the platform.
You need to learn nodejs concepts like async method calls and stuff. If you don’t know what I am talking about then this below video is a good introduction to nodejs:
Keep this as a rule of thumb – don’t enable automatic updates right away. Otherwise, you would develop on one version and suddenly after an update, the project would stop working.
It is not cross platform!!! I’m telling this after a lot of bad experiences. Developing for iPhone and then “fixing” things for Android or the other way around is definitely a pain!
In a way, it is cross-platform and it could speed up your development time. But only for small petty projects. Not for larger ones.