Both as a trigger for flashes as well as Funkauslöser great.

I use the 603er to a 6D and had no problems so far, the flash fires has once worked out a few hundred smoothly, there was not a malfunction when the trigger properly saß.Auch useful as remote trigger, even both going at the same time:
1. YN-603 in hand goes on 2. YN 603 to the camera via the cable, the camera is triggered and at the same time the flash.

And now the best: My 6D does not recognize the RF 603 as lightning. So when I unleashed flashes or the YN 603 put between the camera and flash, I can adjust shutter speeds below 1 / 180s. In a 1/4 performance YN can be used 560 Mk3 hesitation to about 1/320, 1/400 in is no longer sure that the lighting is uniform. With lower flash output can then also make lower times.

Of course I have so no sync on the 2nd curtain, and it is not as reliable as HSS, but when I consider what you yoy. HSS saves, I'm thrilled and would solely accessed repeatedly. :)