Summary: It took me an hour or so but I've now got 4 of these working fine with data rates from 150 to 80 Mbps. The lowest is remote from the other 3 and on a 4-way extension lead, so no real surprise. This is why I've given 5 stars overall. I started out by following the instructions and holding the "link" button in for 8s on the 1st adapter and then running through the house to do the same on the next adapter. This wasn't too successful.
Summary: they arrived the next day from dispatched, opened them up plugged one in downstairs connected the Ethernet wire (which came with it) in to my router went ups stairs plugged the other one into the wall then connected it with the other Ethernet wire (that came with it) into my desktop and it connected instantly the reason i brought these is because i could not even get a wireless signal in my bedroom in my new house which is a good bit away from the router.
Conclusion: Bought these when I'd lost all hope of restoring networking capabilities on my ancient Samsung laptop (think the wireless card's finally died in it), and they work perfectly out the box. Plugged them both into the same wall socket and pressed the link-up button to 'register' them, situated both adapters where I needed them to be, plugged in the ethernet cables and away it went.
Conclusion: I bought these with the fact they may not work in mind but took the risk anyway, how I need not have worried they are superb, I have an old house that the wiring is 20 years old and they work 100%, I now have my PC working as a HTPC from two rooms away, so that's Â£33 vs Â£250 to build another machine, Now lets look at the performance aspect, these are rated up to 200Mbps, the best I've seen is 170Mbps and an average seems around 110 - 160, when I first set up I had both...
Conclusion: I was really pleased with these. We live in an old house with thick walls so wifi is no good and ripping up floorboards to take ethernet cables not much fun either. This works brilliantly. Living in the country we only get a maximum of 10mbps anyway, and the TP-link doesn't seem to affect this performance at all. And yes, you just plug it in and switch it on.