The WW Grimlock and Shockwave busts that I have were dead cheap when a local store was closing down.

The Hard Hero Rhinox statue kicks ass and I bought it for the same reasons as Verno mentioned but mostly for being a character model accurate representation.

To answer the OP's question - They are not useless, they are collector items. How 'useful' they are is really up to the person buying it. They are display pieces so I guess if they are able to do that correctly, they have fulfilled their purpose.

When it comes to how I feel about them - I like them but wouldn't go out of my way to buy any. As mentioned, the two busts that I have were chance buys (cheap) and the Rhinox statue is a unique piece.