Darren Heath is (in my opinion) one of the greatest motorsports photographers around. I must say that in the last year the quality of photos that he has been putting on his site/blog has fallen slightly. I think in his pursuit of unique photos at slow shutter speeds he has started to accept softer photos. However people have to appreciate that the shots he will put on blogs such as the BBC's Big picture will be the more experimental shots, nobody wants to see a hundred identical pin sharp photos. That takes no talent to take.
Have a browse through his blog from the last few years, i particularly like the Canada 2010 gallery:
http://www.darrenheath.com/season/2010/canada-2010/image-gallery#3348
The 1ds is not that uncommon a choice amongst motorsports togs. Carrying a combination of full frame and a crop cameras would give you some flexibility on prime lenses. The 1ds also makes much more sense as a pits/paddock camera, so if you have that camera with you anyway and you don't need the crop factor for a particular shot - why not use a larger sensor, arguably better colours, shallower DOF, higher resolution. In reality even the fastest cars are fairly easy to AF on, most of the distances they are shot at means there is little AF adjustment to track the car.
As for that particular shot of Seb, its not the best shot in the world, however it is different. Who wants yet another shot of him with nothing making it different. I bet you that he has shot LOTS of stock of him in more conventional styles, so what use is another one of those photos.
I am massively biased in my opinion of his work as i am a huge fan of his approach to photography and love most of his work, so i am always going to defend him.