They work - what more do you want?
What you are describing is a video sender not a ethernet to powerline converter.
Something like what you want exists http://www.onevideo.co.uk/product_info.php?products_id=525 don't expect it to be cheap.
When you say you'll "stick to proper ethernet" well that rather defeats the point doesn't it? These devices are designed to allow you to connect ethernet based devices to an ethernet network where there is no direct cat 5 cable connection available. If you had "proper ethernet" available why on Earth do you want to use one of these?
I've been using a set of these since December to connect my showcentre 200 and a wireless access point (in the lounge under the TV) to the rest of the network which has most of it's hardware (and broadband access) in the study at the other end of the house. It works flawlessly allowing me to surf wirelessly and watch streamed HD content at the same time.
Out of interest I'm getting between 60 and 65 Mb/s - the house was completely rewired in 2005 which may account for the difference between my results and those of the author.
I can give these devices a big thumbs up. They do work. My only criticism would be that the blue leds are a bit fierce especially when you have one adaptor stuffed down the back of the TV and the lights down low to watch your favourite movie. A bit of cardboard and a roll of bodge tape cures the only flaw in this product very quickly!