My only fear with the fake a lake (or similar design) is that if you are in the boat and it falls off the boat and you don't realize it, you run your boat dry. Don't know if this fear is justified, but I returned the one I bought. I guess you could always run the boat while you are not in it to prevent this. I don't even know if it is even worth worrying about, but I didn't like it. I agree with everyone that it is easy to make your own fitting for a water hose to connect to the line. If you want to take the easy route (and more money), buy a flush pro.
http://skidim.com/prodinfo.asp?number=DP7