I have used these:
They are pretty easy to set up (outside of running the cable of course) and when they work, they have worked well. The problems I found were two fold:
1) the jacks on the back (where you plug the Ethernet cables in) are not well made. I tried unsuccessfully to crimp my own wires and never could get them to work with the adapter. Tried several different types of connectors. It seems that the jacks are just a bit loose and most of the connectors you buy just aren't good enough despite passing on my cable tester. I bought some 6 inch cables from monoprice and duplex connectors and put those at each end, and had no problem.
2) The signal that gets through is not as strong as a regular HDMI cable. So if you have any interference along the way you could be in trouble. I had an additional problem that while they worked fine going out from my HTPC to the TV's, when I put my AVR in the center, the picture started breaking up and eventually lost the handshake. I ended up having to switch both my sets out for actual HDMI cables. I'm now going to use them for my desktop PC's DVI connected monitors when I rebuild my home office next year.