Upload & Sell: Off
BH mentions that the flash duration is not specified by the manufacturer. I'm gonna say it's at best 50/50, but if your current lighting situation is atrocious, why not give it a go.
Unfortunately, there isn't a cheap way to test flash duration. Broncolor has a meter of sorts that also measures duration. You could make a DIY test, if you have something to compare it to, say a hotshoe flash. If you could get something to rotate or spin at a constant rate, then shot a picture of it with a hotshoe flash with a known speed at a certain power level, then shot the same picture with the m500s, you could compare if its faster or slower.
To be honest though, some of the higher powered lights, Elinchrom 600s, have t.5s of 1/2050th and t.1s of 1/700th. Einsteins are, in this regard, amazing because of their IGBT circuitry. But even they are not as fast as the Elinchrom at full power (at anything below though, they kill the competition).
My point? if full power Elinchroms blur up, then your chances go from 50/50 to slim.
Just my thoughts.