I think it's a very good effort but I agree that the pictures are too small to be of much use. I would rather there were bigger pictures of the standard, general release sets ... and less of the country-specific sets. What would be great would be to have decent sized pictures of the back of the boxes, showing the contents of each set. It would be handy to check what's missing in a particular set you own. Playmodb and Collectobil are great and very very useful but the picture scan quality is rather poor. I know the bigger the picture, the more space needed and bandwith etc, but it would be nice.
As for the rarity system, Id really love to know how it was worked out. According to the book (if I remember correctly) the 3626 set is rarer than the 3627 one, which is hardly the case.