An A grade last year was almost 26% on average across all subjects, leading prestigious institutions, such as Cambridge, to call for an easier way to distinguish between the top academic performers.
So as well as there being more stretching questions in the A-level exams, candidates who obtain the highest marks will be awarded an A* - as is already the case at GCSE level. [As cited at http://news.bbc.co.uk/1/hi/education/7946675.stm]
Hopefully it won't devalue those who achieve high A grades before 2010, when the new grade will be drafted in.
I feel that, possibly, it's a way of maintaining high grades, whilst distinguishing between the top academic students. I wouldn't hold my breath for 'more stretching questions'.