I bought 4 of these to connect a computer's 7.1 output and the 7.1 analog output of a blu-ray player to the same Creative 7.1 speaker set. It did that, with all 7.1 channels being properly separated and going trough the correct speakers.
However there is a constant hissing and not only is the volume much lower, it sounds muffled, like you were hearing the sound trough curtains. So for this purpose it is pointless and would ruin the home cinema experience.
But they were designed primarily for splitting an mp3 player's signal into two distinct stereo signals. It performed even worse. The channel separation was very poor because it once again lowered the volume to the point where it sounds muffled. They made a very nice pair of Phillips headphones sound like one of those pairs you get when you do a bus tour.
So basically, this product is worthless. I cannot recommend it even for the use it was designed for, and considering I bought 4 of these and tested them all, it is definitely an quality issue with the product itself.