Giving the users a choice on every page to revert back to standard is a must. You don't want to tick off visitors because your mobile page was not enough and you don't let them switch back. I've have so many dead ends on mobile sites it is annoying. I don't go back to those sites.
The worst is when sites auto redirect you to their mobile site but the page does not exist. And there is no option to view it on their regular site. You can even manually change the URL because they keep redirecting you to a page that does not exist.
So be warned. There is a lot to design into a mobile site. I live them when they are done right. When done wrong they can be a brand killer.
Btw- Brett- when can we see a mobile version of WebmasterWorld? The width/font of the threads on this site is awfully hard to read on my iPhone. It seems to use a fixed width which does not allow the font size to scale!