Google supplied me with the full family (so far) of 16 faces to examine: a regular and oblique (the sans serif name for a slanted type that's not drawn differently, as with italics) of Light, Thin, Condensed, Bold Condensed, Regular, Medium, Bold, and Black. This warms the cockles of my typographer's heart, because with many different weights of a typeface, you can use differentiation to signify importance or meaning without having to rely solely on placement, size, or other faces. (The sign of a bad design is typically the use of many different sizes and faces. Find a great design, and you'll find remarkable restraint. The exceptions, which are legion, break that rule and prove it at the same time.)
I’m not convinced that using eight different weights of a single typeface in one document is superior to using eight different typefaces. The advantage of eight different weights is that you can pick a subset best suited to the use, not so that you can use them all.