Canonical redirects break a LOT of things even when using
mature desktop browsers, so I'm sure they cause even
more problems on mobile browsers, some of which are about
as developed as IE 2.0.
Some of the bigger problems you see on all browsers
Breaks if your site is accessible via https as well as http.
http://www.site.com and site.com.
Breaks PHP sessions in many cases.
Breaks load balancing such as www1.site.com
I could go on and on, requiring the use of fully qualified
URLs via the redirect or the new "validation" of the base URL
just really screws up a lot of things.
On the other hand, it does help your Google rank, but only
in the land of fairy tales. In the real world, Google already
assumes that http://www.site.com and site.com are the normally the same.
So the actual benefit is .. nothing. Just a huge pain in the
rear, causing all sorts of incompatibilities, for no reason