Housing: grabs not quite as wertig like the real thing, however, is okay.
Juxtaposed (yes, I have also the original) must be to look very closely to distinguish them.
The AF-assist illuminator: makes a very different pattern, as I know it from previous Canon flashes; It usually works.
Mostly: depends on the distance and the camera and lens.
The group mode for cameras before 2012 (in my case the 1D Mk4): Works!
Although was not the big problem, but it's nice when I do not have to change even in the head modes, if I change the camera.
2. Curtain: yes, work in manual mode.
What further fascinates me: the original triggers the flashes in manual mode only when it is sitting on a Canon.
The Yongnuo triggers (from firmware version 1.08) with other cameras, such as a Fuji X100s- and there opens up very interesting possibilities .....
and the setting values are transmitted wirelessly!
(I myself have not tried it, is in the Fuji Forum described as very reliable functioning)
Yes, it's a cheeky copy, but with very nice additional features.
Oh, I almost forgot: has a USB port.
For more updates.
Great device- unequivocal recommendation to buy !!
Update 03/18/2014: Now that I have the X100s own: the Canon 600 RT can be triggered in manual mode through this device.
The change of power takes place via radio: Setting the strength, once on test press (= transmission and it will flash) - change at lightning arrived.
I'm thrilled!