Yep, they're tough. But you slice 'em thin, or you tenderize them with a hammer, and they're fine.
Raw clam? Nooo. That's not for me. But fried, or in chowder? Delicious!
The texture isn't dissimilar to abalone, if that helps. You see one of the parties in the article referring to the clams' "crunchy" texture. Crunchy isn't the right word since it is sort of an INTERNAL crunchiness, but I can't think of a better way of putting it.

Gold is $1,581/oz today. When it hits $2,000, it will be up 26.5%. Let's see how long that takes. - De 3/11/2013 - ANSWER: 7 Years, 5 Months