I'm ready to be that none of the first 3 replies have actually used anything better than average cables.
I have a moderately priced Lava tweed cable, the improvement throughout the sound spectrum is very noticeable. More clarity throughout, more lows, more highs.
At home, the difference is good enough that if it were damaged (unlikely, that thing is VERY well built) I'd get another one I'd pay for myself if the lifetime warranty didn't cover it.
In live environment, I'm not sure how much benefit you'd get from them though.
The bottom line though, is that whilst they are good (well, my lava is anyway), I was very happy before my planet wave cable broke. (Planetwave honoured their lifetime warranty) It's just that the lava cable I have brings that little extra to my ears. Bear in mind it's not night and day - but still noticeable enough.
I've had my Lava for 2 years now, probably will have it for 20 +, so the £40 price tag isn't much in the long run too. I find it better than invoking the PW warranty every other year and going through that hassle. YMMV