If you are tired of writing JavaScript in your templates to get client-side behaviors, the JavaScript helpers offer a simple alternative. Not only do they automate the basic link behavior and element update, but they also provide a way to develop Ajax interactions in a snap. With the help of the powerful syntax enhancements provided by Prototype and the great visual effects provided by script.aculo.us, even complex interactions take no more than a few lines to write.
And since making a highly interactive application is as easy as making static pages with symfony, you can consider that almost all desktop applications interactions are now available in web applications.