"That’s kind of a no-brainer, when you think about it: if you’re going to review an application, it only makes sense that you’ve used it, right? Hopefully, this will do something to prevent the onslaught of bad reviews based only on an application’s description."
On a site I run for work, we encounter the same problem - people providing bad reviews, bad information and inflammatory comments on devices and services they don't have - and have no intention of purchasing. This is an interesting technical solution - and fairly easy for Apple to adopt, since their review platform is tied directly to their backend purchasing systems.
Our systems are unfortunately not so well interconnected - we have no way to identify users who actually have the device, so we rely on good old fashion manual reviewing of content submissions. Some sludge still leaks through, but it's as good as we've got for now.