Personally I never register when I shop online. But we offer registration for our customers who are often businesses who buy repeatedly from us.
Maybe 1/4 of our business is done with people/companies who register. We don't store CC info but our cart could do that. We save only product order info and ship/bill addresses. I know some customers would be irritated if we didn't offer registration.
One thing is for sure. Let customers clearly know they don't HAVE to register to shop and buy.