That is true - they sell it as a logo program to make your customers feel more secure and frankly it is all about making it more secure. So they're not entirely wrong ;)
If you pass all of the audits and do the self compliance check for PCI then its a pretty good bet that you are secure. Have you SEEN the audit? I mean they go down to what router/network/firewall/IDS systems you use, how you lock down your accounts, how you rotate passwords, how you separate business process es and then the automatically check your applications against known vulnerabilities.
I think the problem with the sales pitch is they sell the concept because most decision makers interested in the product know squat about the technical aspects.