I've had an iMac, MacBook, Mac Mini, three iPods, two iPhones, two MacBook Pros from work (registered to me), an Airport Express and an Airport Extreme and this is the first survey email I've received.
That said, it is just a standard satisfaction-oriented survey, but it's likely to be used by Apple as a weapon in the PR war ... assuming the satisfaction ratings are high enough. And used internally these surveys are always useful.
And unlike online surveys, at least it will be only iPhone 4 owners who'll respond.