AB works well on the iPhone/iPod Touch/iPad as it is. The one big problem is the number of links on each page. There are probably over 50, which does not lend itself to touch screen technologies. It is easy to catch a link, when you merely want to move about a page.
That is only really a problem on small screens. AB on the iPad is excellent, no problems, and Tablets look like taking off in a big way.
A lot of sites that have produced mobile apps, the result is a very poor user experience.
The BBC News app is very weak when compared to the main site. Newspapers are especially poor.