Dustrider's points are excellent.  I'd like to add also that another great benefit of Octane vs. Luxrender or some other engines is not only the speed difference, but also the ability to render biased OR unbiased lighting kernels in different "modes".  You can get Luxrender-like PathTracing, or GPU-optimized PMC kernel, which handle refractive/reflective caustics and other problematic physics more efficiently.  There's also a Direct Lighting mode, which is the fastest mode, and provides biased results, similar to Vray, but much, much  faster in most cases.  Seperate passes for compositing are also available (llike Z-depth pass), and render almost instantaneously.  It would be considered an impressive render engine, even if it weren't GPU based.

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.