Since we come from enterprise environment Java is the second mother tongue to us and I have got accustomed to mighty autocomplete and refactoring features of eclipse. The main reason for diverting from Java would be purely of taking intelectual pleasure in learning new things and checking if python/ruby frameworks live to the expectations.
We did some contract work on french social startup using a very lightweight web framework called Stripes (http://www.stripesframework.org). It was much better experience that using component based UI frameworks like JSF.
Needless to say - for quick web hacking I still fall back to PHP.