value() is defined on Elements of type
:attribute and :text, but not :comment.
For :comment, you use to_s.
(to_s may work for others, as well.
Haven't tried.)
Element
.node_type --returns a symbol
:attribute -- use node.value to get text
:comment -- use node.to_s to get text
:text -- use node.value to get text
:cdata (maybe. not verified)
:element -- ...