Thanks for the kind words, guys.
I don't really want to re-write my whole article here! But I agree most of the time Photoshop is a much better option than double exposures in camera (which offer much less control).
The one area that the double exposure is better (in terms of end result) than photoshop is sometimes in the subtleties of the combining of images.
Here is a crop from the shot. Look at how you can see the reef through the fin of the triplefin. I think that this would be tough and certainly not much fun to do in Photoshop. Work of a fraction of a second in camera! (excuse the image quality - it has been uprezzed to 20 MP, then cropped, save as jpg 7 and then reopened, resized again and saved for web!!).

This natural blending is nice.
Alex
p.s. The EXIF comes from the first image, Paul.