Dracos,
Please, it’s not application/xml+html, it’s application/xhmtl+xml.
I’ve never seen it so often misquoted as since the IEBlog made that mistake “that time”:http://blogs.msdn.com/ie/archive/2005/09/15/467901.aspx , later to be “repeted by the WASP”:http://www.webstandards.org/buzz/archive/2005_09.html#a000576
And I agree with you that this problem is big. To me it sets back real XHTML another 5 to 10 years.