My first cavalier didn't have them. The breeder has having them removed very young, but she had one puppy die after the operation and after that she wouldn't have it done anymore, so 10 months later when I got Merry - she had her dew claws. Merry hasn't had any problems.
I did have a bassett hound with dew claws and she lived to the ripe old age of 14.5 years old. She did get a dew claw caught once and it bled. I took her to the vet and it was a very minor injury and not medication or other work was needed.
Charleen and Cav's: Pippin (ruby male), Merry (b&t female), Luke (blenheim male) & Jolly (tri male puppy)