I'm fairly new to the world of scoped rifles (most of my shooting experience is with shotguns and smallbore rifles with open sights).

I've been doing some reading and research to select a scope for a 7mm mag I just ordered. I see that Nikon offers an Omega series of scopes for muzzleloading rifles:
http://www.nikonsportoptics.com/product.php?group=16&subgroup=10&product=8 402

The specs on this scope seem reasonably comparable to most other mid-range 3-9x40mm scopes, with the exception that the Omega has an outstanding 5.0 in of eye relief. The field of view is marginally smaller and the price marginally higher than comparable centerfire scopes, but that's a trade I could live with for an extra 1" o 1.5" of eye relief.

So, my question is: other than marketing hype, what distinguishes this "muzzleloading" scope from a centerfire scope and what would be the reasons (if any) not to use it on a centerfire rifle?