Sony HVL-F43M flash (which seems to be a better "fit" on this camera) ... originally I wanted to go for the HVL-60M but gave up the idea after trying it on the a7, it just looked ridiculously huge on this small camera.
Even F43M would be awkward on camera, and I hate that flash-on-camera look. Even with my 5D III, if at all possible, I shoot 580EX II off-camera on gorilla pod/portable stand via either Yongnuo 622 or Canon 90EX (smaller venue) in TTL mode. Looking to do the same with Sony A7R, I was shocked find NO TTL wireless triggers available. I then looked at the smallest Sony flash HVL20M as TTL-trigger, but many other people must be thinking the same because they go for full-price on fleabay. I don't like to miss shots by trying manual wireless triggers, but I tried my Yongnuo RF603 manual trigger on the Sony A7R, but Sony's new "standard" hotshoe really isn't standard and RF603 wouldn't fire.
The strobist limitations along with the effort it takes to move around the flex focus point really didn't let me enjoy the shooting experience, e.g. having to push a button in awkward location to activate the AF point, then using the two stiff dials, one in front of camera and one behind (!), to move point vertically and horizontally really takes away from the joy of shooting and simply too slow to move the AF point. A7R really needs a 4-way joystick like 5D III does.
And it seems like some new "problem" is reported weekly for A7R, e.g. shutter vibration, "light leak," lossy RAW, not really weather-sealed, etc. The lossy sony RAW thing especially bugged me in the back of mind, especially since this kind of thing really shouldn't happen if you are aiming for the semi/professional photography market. It's also something Sony can fix *IF* they wanted to, but they don't seem willing to do so, just like they are not willing to admit to the FVL60M flash overheating problem after 20 shots.
Oh, well, it saves me $3K, which I will save up for the next Canon purchase. All right, Canon, you still got me, with your "poor DR" and all