PC World has it's place in the market, it offers brand assurance for people who might not otherwise understand computers. Yes, you pay more but you're buying into the idea that no matter what goes wrong, you'll get sorted.
Case in point, my wife wanted a new PC, as her old one had died a sudden death. Going into PC World meant whilst she paid more for the item, she could take it away there and then and it was covered. 18 months later, when we discovered it was the wrong item (due to a dead graphics card and getting sent the one from the sales reciept rather than the unit we had), we got the price difference refunded (about £200, handed out in cash on the strength of the reciept and finance agreement).
So yeah, maybe not the best or the cheapest, but they still definately have a place.