RJS doesn't work

<%= collection_select "user", "id", @users, "id", "firstname",   { },   { :id => "selectUserList", :class => "width100" } %>

<%= observer_field 'selectUserList', :url => { :action => :select_user } %>

This will automatically submit to the given URL and pass the selects value in parasm[:user][:id] and it works with RJS from what i know an experienced.

In fact i wonder why remote_function doesn't, as the API states it can have the same options as link_to_remote, which sounds like "you can leave out :udpate and use RJS" ... might have a look at it's source to see what's the reason.