I'm currently using a Merlin Black Widow with my TV and a Russ Andrews Powermax with my PS3 and, although I didn't think the difference was astonishing in picture terms, it cleared up a tiny bit of noise I could see on some aspects of the picture so I've kept them for that reason.
I also had the Clearer Audio Silver-line cable for a little while powering my Onkyo receiver and, again, I did think there was an improvement, but in this case, not £200's worth of improvement so I sent this one back for a refund. I'm currently deciding whether it's worth trying a cheaper cable for this or not.