I might as well put my 2 cents in also. I have a 2012 ElectraGlide Classic & am running 100% synthetic Amsoil. I appreciate the fact that I can run 100% because I couldn't do that on my old Gold Wings because of their wet-clutches. 100% synthetic can make a wet-clutch slip. On this Harley I don't have to worry about that being the crankcase oil is separate from the clutch. For those of you that ride a lot in the winter, keep in mind that synthetics will pour immediately down to -60Fahrenheit. The plus to this is as soon as you start your Harley even in the coldest of temps that synthetic is flowing immediately, no dry startups.
Just my two cents.
I run syn in my primary, I have a wet clutch. It doesn't slip. I'm actually thinking about going back to regular oil in my engine crankcase. The mobil V-twin oil I use is about 10 bucks a qt, and even though it seems to run cooler, I can get 5 qts of Castrol for 17 bucks. By 3K miles the oil is black and looks like it needs changing. I don't feel good about running oil for 6K in a bike.