It seems that the format.html, format.xml, format.* response code has a slight problem with it. It seems that it is now taking any request for format.html and assuming that means... "#{actionname}.rhtml"... and that's definitely not cool for .haml and .mab people.
Instead, we should append an r for xml and rss.... and leave ActionView's clever "template finding" code go to work to determine what we should do for html.
I don't think its wrong to assume that AV should make basic assumptions that without a specialized ending, that we are talking about some sort of html renderer. This was the assumption up to a few weeks ago when the code in there got a little "cleanup" into a one-liner. Which, indeed is much prettier, however it leaves us delegate render people in the dust.
The patch is up and ready to go!
Its a simple exception for :html.
http://dev.rubyonrails.org/ticket/6281
Cheers!
-hampton.