I can often hear a difference between different pairs of identical interconnects, let alone a different model or brand.
A person with perfect pitch or music training is going to notice small changes more than someone who is tone deaf or un-schooled in music. I think hearing ability and skill plays a part in this difference in opinion. Anyway if someone is happy with their Bose Wave Radio/CD player, more power to them and I am sincerely happy for them. I just wish Paul Harvey on the radio would not claim his son the "Audiophile" loves his and has tweeked it further.
To use a golf analogy: Tiger Woods has custom clubs made to his exact specifications. They cost many thousands of dollars to make. With his skill they enable him to control ball flight in inches. If you're a 24 handicap, will a pair of megabuck custom golf clubs make much of a difference over a $300 pair from Sears? Probably not. They would be a waste of money. Does that mean they are a waste of money to a serious player?? Many times one stroke lost will cost a pro 10 to 20 times what the clubs costs.