It's a niche product, providing primarily just what napamatt mentions: tier point earning. If you fly a couple of times a year to the UK with VS, in PE say, the CC will make it easy to keep Gold on VS and thus use the clubhouses, revivals, etc, even if you don't fly much with VS. While doing this, you'll also probably earn enough miles to upgrade to UC consistently, and still make out even to a bit ahead.
If your flights are going to be in J anyway, or you fly regularly with a US airline internally, or you fly enough to get AU anyway, I would probably not recommend the card. Flying Club is not a program that provides sufficient benefits in further mileage accumulation (especially from the US) as the use for the miles is somewhat limited. Things have improved a bit with the VX connection, not enough IMO though.
For me, the card allowed me to split my TATL flights with UA and still requalify for gold (as well as make 1K last year on UA). Guess what happened? I found myself traveling when VS was going through the motions (motioning mostly in the wrong direction), and UA was getting a bit better. I found that I could abide UA, and in some ways liked them better, and that you can't beat the ability to walk into a (sometimes great, if never quite LHR-CH-like) lounge in almost any airport in the world on any ticket. So I switched. Both airlines, and credit card ...
Conclusion? I'm not sure the card was a great idea, I don't think it won VS substantial new US biz, and may have lost them some, and marketers sometimes aren't very good economists and they don't think through their incentive schemes carefully enough.
