Jordan.
I had set the attribute name (:attribute_name => :disable_dependencies) in the option.   Because this is a multi value option I don't ever see attributes[:gem_disable_dependencies] as being available.   When I dump the attributes themselves I see this ':gem_disable_dependencies=>nil'.   I do see attributes[:gem_disable_dependencies_list] as getting set though (:gem_disable_dependencies_list=>["clamp", "cabin"]).   Would you prefer I refer the attribute name as what I think is the default is 
'attributes[:gem_disable_dependencies_list]' and not override the attribute name in the option.

or

set the attribute name in the option via 
:attribute_name => :gem_disable_dependencies

Or some other course of action.    
Thanks. Derek.