If you have crappy power and cheap power supplies in your components (most TVs, low-end receivers, DVD/BR players, etc would probably qualify), then you may see/hear a difference with power conditioning.
The thing is, power conditioning is basically what each component's power supply is supposed to be doing. Excessive noise in the power line could be more than what a particular power supply can handle, in which case power conditioning of some sort MAY make a noticeable difference.
However, to make a blanket statement that EVERYONE should go buy the most expensive conditioner and surge protector they can afford is a bit of a disservice.
The thing is, power conditioning is basically what each component's power supply is supposed to be doing. Excessive noise in the power line could be more than what a particular power supply can handle, in which case power conditioning of some sort MAY make a noticeable difference.
However, to make a blanket statement that EVERYONE should go buy the most expensive conditioner and surge protector they can afford is a bit of a disservice.