What bothers me most about this is that if you go to www on a mobile device, it redirects you to m - that's great, and probably the "right" thing to do. There is probably a "View Desktop Version" link on the mobile page, somewhere. But if you go to the m subdomain on a desktop device, there's no easy way to get to the desktop version without manually changing the URL. If you can redirect from www to m, surely you can redirect from m to www when appropriate.