Thanks for the answers. I've already found this links but it seems that RJS isn't detailled on the web...
I agree... It seems like RJS is considered a marginal rails feature.
What is the easiest framework to discovery (jQuery or Prototype) ? I saw that Prototype is included by default in RoR 3.
I had the same problem... RJS was really attractive to me too because I've never been very good at coding
I began studying jQuery. It's fun, simple, intuitive and extremely powerful (from ui to more "dev" stuff like ajax and json).
Prototype is included in RoR because it started from Rails itself. Even so, I personally find jQuery much more easy to learn.
Don't forget there are also other js powerful frameworks (like dojo and mootools), so maybe you should look around to find what fits your coding style. If you choose jQuery, there is an easy way of including it in a rails project: jquery-ujs
Obviously when you leave Prototype, you need to leave RJS as well.