ActionView#url_for generates escaped URLs by default, whereas ActionController#url_for doesn't. They should be consistent, and I believe that ActionController's behavior is correct here. The escaping is most noticeable in a call with multiple query parameters:
view.url_for(:controller => :foos, :action => :do_stuff, :this => 123, :that => 456)
generates
http://example.com/foos/do_stuff?that=456&this=123
Note the escaped ampersand in between this and that. Named route helpers use url_for and are thus also affected.
--Phil