I have owned this device for some years.
It is for the most part a great device, and I find the picture quality to be absolutely superb although I have had some problems with it, some of which I have solved and some not.
1) Our microwave renders this device unusuable. It makes a frighteningly loud noise and completely scrambles the picture when the microwave is on.
2) My wireless LAN interferes with the picture too. I get a regular pattern of lines which on certain channels is better than on others, but never goes away. We live in a quiet town in Berkshire now, when we were in London I would often get other interference too.
3) Any picture signal with a lot of white in it (flame, or bright lights, mostly adverts and opening credits, fortunately) causes loss of vertical hold on the picture momentarily. This has never been a real issue.
4) The "Mounting the device above your video player or cable box" just doesn't work for us. I had to use the extenders, which means only two devices. I get around this by having the DVD player running through our Sky box, and the Sky box running through the VCR. This means that whichever one of these devices is on, will play a signal. I have ended up only needing one channel from the device this way, so the manual switch is no issue at all.
5) Our cable box would not work because the TV Link won't route the correct frequency of IR. Now we have a Sky box, and that also (maddeningly) has weird behaviour, and will work once or twice and then "jam" until it has been manually turned off and on again. Sadly I have to go downstairs to change Sky channels, but for watching movies in bed, and controlling the VCR/DVD with my universal remote it is a great device.
6) An added plus, if you have a DVD player like ours that plays CDs is that you can get your music beamed somewhere else too. Either on your TV speakers, or if you plug in a set of PC speakers, you could get more decent sound.