That's something I've never seen before -- the seller information block doesn't display the seller's feedback! I had to click through to get to a page that displayed their FB rating: 99.3%. Looks like quite a few people have trouble activating cards from this provider. If this were another direct-from-eBay electronic offer, I'd buy without a second thought. But a physical card delivered through USPS? Something's bugging me here.
It was advertised by ebay, so I would guess it is OK. Plus you always have buyer protection if it does not work.
Apparently you get a warning if you buy these with multiple accounts using the same paypal. I just got 3 warnings. The offer said one per ebay user, so I took that to mean ebay account. Whoops.