I'd read a lot about the 'fact' that, since HDMI cables are all digital, a more expensive cable wouldn't cut it. So, since I needed two cables, I decided to take the pepsi challenge.
Bought one of these QED Qunex - £35 and a (still very good) Techlink Wires cable - £22.
Set the PS3 up to our (not even hugely expensive) Samsung flat panel and, with the same still picture on the screen, switched between the two cables. Now, it was no use me taking the test (as I knew which was which) so I got the wife (who is not technically minded and purports to not being able to tell mp3 from CD) to look and tell me what was best.
I was surprised how resolutely she chose the Qunex. Her reasons (and I agree) were that, while both pictures were sharp and free from any artefacts, the colours from the Qunex were just truer and the gradients smoother.
Not sure what makes it better. I presume the higher quality manufacture reduces the need for the screen to perform error correction on the signal, but I'm no expert. However, I know what I'm seeing and it's definitely better.
So, in summary. This is noticeably better than even a quality £22 cable, even on a regular 720p LCD TV. Given that, it's going to be MILES better than the piece of cable they package-deal in with your new PS3/Blu-Ray player. For a sub-£1000 TV, I would have thought this is as good as you're going to want to go. I really doubt you'll see much difference with a £200 cable. Oh, and remember, this is just reviewing the Qunex - I'm not vindicating other rip off cables (Currys and your £80 Monster cable nonsense!).
Hope this has been of help, it really is worth the money.