Image quality results have been added to the Sigma 150-600mm f/5-6.3 DG OS HSM Contemporary Lens review page.
Here are some comparisons that you might find interesting:
Sigma 150-600mm Contemporary Lens vs. Sigma 150-600mm Sports Lens
Sigma 150-600mm Contemporary Lens vs. Sigma 150-600mm Sports Lens (Sample 2)
Sigma 150-600mm Contemporary Lens vs. Tamron 150-600mm VC Lens
Sigma 150-600mm Contemporary Lens vs. Sigma 150-500mm OS Lens
Sigma 150-600mm Contemporary Lens vs. Canon 100-400mm L IS II Lens
Sigma 150-600mm Contemporary Lens vs. Canon 600mm L IS II Lens
B&H has the Sigma 150-600mm f/5-6.3 DG OS HSM Contemporary Lens in Canon mount in stock. Nikon and Sigma mount versions can be preordered.