Dog hair and our dark grey couch don't mix too well — but when my wife and I are watching TV on the couch and our dog gives us the puppy eyes and begs to join us, it's pretty hard to resist. So we let her up, but with one requirement.
We bought a FurHaven Pet NAP Quilted Fur Rug for $23, and only allow our dog up on the couch when the rug is in place. It's washable, and keeps the couch much cleaner than if we just let her up as-is. The rug protects the couch from her claws too. Really any old blanket or sheet will do; it's just a matter of training your pets to only come up only when the couch is protected.
Somebody looks comfy!