your only going to hear bad things about CPW on here. You will never hear of the the people that had great customer service as there will be no need to be on here.
Another words try them out, they may surprise you!
I had a great CPW experience today, the assistant was really friendly and went out of his way to go through some obstacles put in his way by the CPW/O2 systems to get me my 32G iPhone 3GS booked for pick up at store on Friday morning. He did say that they had been busy and he expects lines outside the shop on Friday!