Rails - Apr 2005 - setting nested attributes and displaying nested errors

does anyone know if rails handle handle nested attributes on forms?

say I have a user with an address (uses composed_of Address)

I''d like to be able to set all attributes of user (including the
address
attributes) all in one step instead of initializing the address then 
setting it to user.address

it would also be nice if form tag helpers also picked up the errors from 
address (if it wasn''t using composed_of but has_one/belongs_to) when 
using error_messages_for

have have you guys handled these types of problems?