I use it in both of my systems and I am unaware of any audible effects, even when I turn it on/off/on.
I use it for audio - a NAS in one room with one adapter, another to a Mac Mini connected to my DAC. I did get some network lag at times, which required some network tinkering (prioritizing traffic between the two powerline adapters in question, as I have another elsewhere, which helped a lot). I also use software capable of memory playback to minimize whatever is left. I'm very happy with the results.
Sometimes "power line" products can cause problems for audio, especially if you have a good system that shows flaws easily. I also think that grounding issues can become an issue. While I don't usually recommend power conditioners, sometimes when dealing with poor eletrical issues, they can solve some problems.
Network data is delivered in packets, so the problem is probably not with the data signal, but from the electrical and mechanical interference.
What devices and DAC are you using? You might want to just use a wifi router and extender to get data to the area, but wifi connections can also have problems depending on how you are using them.
I'm using Netgear WNR1000 RANGEMAX 150 WIRELESS ROUTER - provided by Comcast for free, actually, with the modem rental. Their support people tell me that the more expensive models don't have better coverage but the literature does tout the better models having better coverage - who to believe?
There are two walls between my office where the modem is and my Squeezebox Touches in living room or master bedroom.
The problem arose recently which leads me to believe that perhaps a neighbor purchased a device that is interferring.
I'm toying with various solutions, such as ethernet over powerline or over cable coax, or using a wireless N adaptor to allow the Touches to get their signal over 5Ghz rather than 2.4Ghz (which would entail upgraded dual frequency wifi but I don't mind doing that...). I'd probably end up buying N adaptors for my computers too - not too expensive but extra gadgets on top of what I already have are a PITA.
I read several comments in the forums about wireless causing sound problems. I couldnt believe how much better it sounded with the wireless turned off. I started investigating alternatives and ended up with the netgear power line:
I have turned them off and on many times and never have I heard a difference. I will not go back to using wireless after all the problems I had with that technology with drop-outs etc.