Philip,
That sounds like a pretty decent deal to me. If you go to the Orvis website and find the SuperStrong Plus tippet, it shows how it compares to the "old", regular SuperStrong tippet. They have a chart comparing the two. They use an Instron machine for testing their tippet strengths...so that is all pretty legit. I wouldn't be afraid to take that deal on the SS+ tippet if I were looking to resupply my tippet.