I have been looking at appcelerator it seems pretty fine! Without a doubt, one of the advantages of appcelerator is its support for multi-platform. I am interested in building a
If you only focus on develop apps for Android platform, I recommend you should use native Android (Eclipse + Android SDK as you said) instead Titanium.
Reason: Titanium is suitable if
You want to develop apps quicly, or
Your apps is simple, or
You see Java is so difficult (maybe :p ), so you choose the easier (Javascript of Titanium).
And here is the reasons why you should use native Android instead Titanium:
You want to develop a complex app, or
You want to customize app appearance. It's very important. Imaging you make an app for client, and they need their app to be customized for more eye-catching. Choosing Titanium means you must use their control, which lacks of ability to customize. It'd be better if using native Android that you can customize everything you want.