We bought some for our older (now gone) dogs... they liked them for a few days, then didn't think too much of them. Denna also didn't think much of them - until she got a split one from my sister for Xmas. THAT one was AWESOME (I think she likes my sister more than me!).
After she had the split one, she decided the whole ones weren't so bad, and did gnaw one down to a size we had to toss. We got her a big split one, but that's still not as tasty as the one she got for Xmas. I've heard if you soak them in broth, that will get the dog's interest... we might try that, since otherwise, Denna goes after the plastic toys, and rips small chunks off of them to swallow.