> Sorry if I'm missing some point here, because I'm a Ruby newbie, but  
> is that correct? I mean, seems that we need to write more code with  
> this kind of behaviour.

I was quite puzzled by this behavior too. So in Rails I use a module  
called class_inheritable_attributes.rb. It's a bit inconvenient, but I  
usually wrap all calls to this lib in pretty accessors anyway, so it's  
not that big of a deal. And very helpful :)

http://dev.rubyonrails.com/file/trunk/activesupport/lib/ 
class_inheritable_attributes.rb
--
David Heinemeier Hansson,
http://www.basecamphq.com/   -- Web-based Project Management
http://www.rubyonrails.org/  -- Web-application framework for Ruby
http://macromates.com/       -- TextMate: Code and markup editor (OS X)
http://www.loudthinking.com/ -- Broadcasting Brain