Exactly. At best, an inefficient energy storage technology.

Edit: the difference from fusion (which is a primary energy source) is that in fusion your starting reactants are available. In this case, you'd have to spend lots of energy in a heavy ion collide to create the initial reactants from scratch.

Also, this type of matter is experimentally disfavored in the same way as strange matter: if quark matter was stable, all neutron stars should have converted to quark matter already, but measurements appear to be consistent with them being made from ordinary matter.