Or are they just useful for looking cool. I was thinking of having one of the death hounds at Castle Volkihar become my trusty undead pet.

They are as tough as a Husky but they are undead and do frost damage. Better than other dogs but not as good as Trolls or other followers

Good enough for me.

Way too weak for my tastes, for me if even one strike clips them round the hindquarters they are done..and I dont like havin loads of dead followers so I just left them.

I would leave them out-I see them as too much of a hindrance than a help. They didn't really do much.

lost one to a freakin troll...so the last one stays at home

Their damage output is decent, their health is pathetic. One accidental destruction spell and it dies.