Hello,
I write in ruby for few weeks and I have noticed that in ruby I use 
class (static) methods more often than in "traditional" languages like 
java or c#. In java I use instance methods for two purposes - 
maintaining object state and to use polymorphic behaviour. In ruby 
polymorphism is available to class methods as well as for instance ones 
so I don't see need for using instance methods in stateless classes (for 
example typical application / domain services).

It is common for ruby programmers or maybe I have miss something?

Best Regards,
Micha