It is the most expensive canon flash. It is a unique design, but I am not sure the price is justified given the features and power of the unit. I am now on my second unit. The second repair of the first unit would have cost more than a new flash (all internal electronics fried). This after approximately 30-40K flashes, which is not what I would expect from a pro-level tool. 100-200K would be more like it for a first small repair. I have used this flash for several years with Canon 5D2 and now 5DsR, mainly with Zeiss 100 mm Makroplanar and the MPE 65; a few on the Canon 180 macro. It is a unique flash designed for macro work. TTL works fine, the spiral cords are a bit short for the MPE at higher mag, and at >3:1 the flash with the provided adapter illuminates the background, but not the specimen. Then the flash heads have to be mounted on separate cold shoes (Wimberley plamp, RRS brackets, or similar). This is also necessary for indirect bounce flashing. The controller can also be connected with TTL cord (Canon original or Flash Zebra for alternate lengths) to provide more freedom to position the heads. Ratio control and manual adjustments for z-stacking work as advertised. The light is very harsh without diffusors, which are an absolute must-have accessory. But even then it is occasionally too harsh and bounce flash must be employed. The built-in focusing lights are nice in theory, but turn off too quickly (10 seconds or so). An on/off switch would have been better. Finish is the usual plastic housing for speed lights. I do a lot of outdoor photography and do not baby my gear. There have been no cracks or other stress damages, just scuff and scrapes. Overall: must-have for serious macro, but it does not give high quality results "out of the box". It takes quite a bit of time to get used to it given all the adjustment options (position, angle, rotation, power, ratio, exposure correction). Much better than ring flashes, as it allows more sculpting of the object.