I think having more than one is great, I really do think that they thrive on the companionship of others of their own species. I also find that older dogs who have never lived with other dogs seem to have less socail skills with other dogs, sort of like they have forgotten how to communicate with them. I have 3 and plan to get one more (am waiting for a maltese puppy) and we also have the dogs of friends and family visit often.
I've never had any real problems introducing them and have found that they take to the newcomer really quickly, especially if its a puppy. Just make sure that when the new pup is in the room you give your older dog lots of extra fuss so that they assosiate the newcomers presence as a positive thing. They also might appreciate some time alone with you occasionally.
Obviously everything is double the cost.
__________________ Indy, Benjamin and Malachi   There is no psychiatrist in the world like a puppy licking your face- Ben Williams |