As regards the power factor improvement devices what they propose to do makes no difference to your bill anyway as you pay for kWh, the reading for which even a real power factor improvement system wouldn't change.
Most new devices and in particular Energy Star devices have PF correction built in as applies to that single item.
If you have several industrial sized motors of a few hundred kW each in full time operation in your home and you are being billed for kVAR then PF correction would save you some money. For the other 99.9999% of us it is a complete, total waste of money.
Like I mentioned in a previous post, industrially I have used this type of device but in those plants we used much more power in an hour than most people consume in a lifetime.
This is just a huckster thing - if you want to make a thief or a fool happy then OK buy one but don't expect any bill reduction or improvement of any kind.