I'm very happy with the performance of these powerline networking plugs. According to the software I downloaded from the Devolo website the best connection is always near 200 mbp/s, the worst around 60 mbp/s which is still faster than my broadband speed, I would like to note that performance will vary from building to building so you may get better or worse speeds. However there is one small problem, all the units emit a high pitched background noise while they're on. This is not caused by faulty equipment and is normal according to Devolo's technical support.
The background noise is not particulary noticable normally for example if you're talking to someone or you have a tv switched on and I've had people round who cannot hear it at all. In a quiet room it is enough to stop me sleeping unless I turn off the powerline plug that's about 5' from the bed.
Whether or not these plugs are for you depends on your hearing range and tolerance for background noise. Personally I think I shall be returning the product and switching two single and one triple plug (Devolo technical support told me the 500 AV units do not emit the high pitch background noise), I'm fine with the two plugs in hallway and the living room but the third plug linking my pc is the quietest room in the house and the high pitched noise can be a bit wearing.
Having moved to fibre optic I was disappointed I couldn't do run my youview box etc but using the three adapters, everything is working, WiFi is set up and I can spend more time in the garden room with my laptop! It was easy to set up and although not cheap has given me the access I needed throughout the house.
Functions well for us in our widespread house and with an office in a more distant building in the garden. Speed could be better (we all say that) but is by far the best we can expect in our circumstances.
This is probably a very good product in the right house, unfortunately they didn't work for me. I needed to extend my broadband to both the study upstairs and to a smart TV in the lounge, I thought that these adapters would be the ideal solution, but be warned if you live in a modern house. It seems that I kept picking up next doors sky network instead of my BT infinity, this was actually taking over the hub as well so consequently my WiFi was then rubbish as well. Download and upload speeds were only around 1gb. I have now run an Ethernet cable from the hub to the study and my PC now achieves 17gb upload and 42gb download and no interference to the WiFi. Just got to work out how to get signal to the smart TV now.