I think of it as empowering to the "patient" to be called a client particularly if they're in a rest home or a person using primary health or mental health services. In New Zealand people using mental health services have many titles I guess you could say, they can be called clients (which is the most common term used amongst nurses), service users/consumers (which is the term used in ministry of health documents) or patients. I think the main reason names alternative to patient are used is to transfer some of the power to the client and it also helps them get out of the sick role. If someone has a mental illness, they are most likely going to live with it for life in varying degrees of severity, therefore if they are called clients it may help them to see that they are 'regular' people and they just also happen to have a mental illness. After all of this rambling I guess I'm saying calling "patients" client's is a positive thing.