The focus of Aptana is development of Ajax enabled web applications. The Aptana IDE is based on Eclipse Rich Client Platform, and ins available as Standalone Application and also as Plug-in for Eclipse IDE. Both have the same features set. And it is of course perfect for me, because i try to use Eclipse for everything (And it it possible ;) ). To install the plug-in use this Update-site: Aptana perspective.
In the created project you will find already working examples wit the core libraries you has selected in the wizard before.
Finely here is an screenshot of auto-help, and auto-suggestions. This looks real powerful at for me.
Aptana is a new IDE, the current version is 0.2.7 but it already has some interesting features and it the best for me and my Java-scripts. Aptana rapidly gains community, and i thing this project will succeed in the future, and do it already right now. With new versions of Eclipse PHP IDE and Aptana, developers have, open source web development oriented IDE of the first class!
Update Dez 2015: Screenshots are lost, so removed. Article is not actual anymore, but i left it for the history...