On the same XMP 1.3 programmed timings of (9-11-10-28) and with a raised 1.75V VDIMM set in the bios, we managed 2282MHz @ CL9.
2400MHz on CL10
2520MHz on CL11 (Effective memory bandwidth not worth the effort for 24/7 computing)
Using lower latency/higher frequency memory does help speed up some applications, albeit not as drastic as a CPU or graphics card upgrade. A quick check on Newegg shows the G.Skill ARES 16GB 2133MHz kit retailing for US$149.99 while the average 1333MHz value ram sells at around US$90. Considering that the target audience is high end enthusiasts who most likely have relatively expensive processors and graphics card(s), we find that this price premium is small in the whole scheme of things.