The declawing operation itself is the human equivalent of removing the first joint of all your fingers. Many vets feel that the lack of these joints impairs the cat's balance and can cause weakness from muscular disease. Declawing also makes a cat feel defenseless and can affect their personality, making them skittish or nervous biters. In rescue work, we see many declawed cats that have been given up by their owners. Why? Because these cats still had behavioral problems that were worsened by not having their claws.
There are alternatives to declawing. Exercise and play with your cat regularly. Give him a scratching post and teach him to use it. Trim your cat's nails on a regular basis. And, of course, talk to your vet or cat-owner friends about ways to "train" your cat to exercise its natural instincts in non-destructive ways.