Since I buy reluctantly twice and prefer something even more spend, for a product for a decade (and more) without objection or "failures" and "gnashing teeth" (because it is impractical or "processed cheap") used, I have it to me "indulged". The little brother 430 EX II would have perhaps done, but no, that money is well spent, not compromise, and later: "Had I but ..."
I recently tested it extensively then the Mercedes-Benz Museum (Stuttgart) at a EOS 40D with EF 17-40.
The performance was estimated based on the guide number 58, but I was impressed with how deeply extends the light of the flash in windowless, shady exhibition halls. You manage relatively easily by indirect lightning (quick adjustment azimuth / elevation, robust setting by button), use of (integrated) diffuser and the (integrated) Catch Light (white surface as a reflector) the darkest games and the shade of the precious vehicles without unsightly reflections lighten in the paint.
The handling is intuitive, the function of most knobs self-explanatory, at least take a look in the manual confirmed the assumed function. The buttons are rarely required (defaults, if necessary adjustments), especially when operating the flash in E-TTL mode. Most functions can be anyway set via the camera's menu. So: Do not panic ...!
Good to know:
* The flash comes in a black cloth bag with Velcro. In an internal compartment Minitripod infected by the flash of the camera set up separately. Impractical: The bag has unfortunately they attach no loop or possibility of a camera bag, belt or other (eg with Velcro).
* The flash can be in most cameras do not "innately" remote trigger (wireless TTL control), only EOS 60D and 7D can do that. In my one must have a wireless remote release for sale (good there from about 55 Euros) or a second flash to the camera as a "Master" (the mitblitzt, or may not) use. A studio photographer with budget will probably a (200 Teuronen) ST-E2 afford IR Remote Shutter ...
* The "zoom" of the integrated scattering mirror (automatic adjustment of the illumination angle to set focal length of the lens) will only work in position 0 ° (parallel to the optical axis), without the use of the lens and in the range 24-105 mm (real focal length, so in Crop factor 1).
In other cases the scattering mirror is adjusted to an angle which is equal to 50 mm real focal length.
(Max. + 90 °) * With a minimum of -7 ° azimuth can also be very close to objects (0.5 - 2 m) flash of right, so that the bottom of the image is illuminated (flash axis crosses optical axis).
* The flash of course dominated special modes, the most important: flash synchronization at the second shutter curtain ('freezing of dynamics "), strobe (" movement "), manual flash output reduction, flash exposure bracketing (FEB).
* 4 Eneloop batteries about a 2000 mAh survived the 6-hour lightning storm without significant losses, which remained in his pocket "Reserve". With batteries installed, I could not detect any adverse emphasis or "rollover tendency" despite insufficient battery grip at the relatively "small" 40D. The flash is voluminous, but "does not fall into the great weight", the wrist has not complained.
* It rattles nothing, nothing wobbles, the hot shoe is splash-proof and quickly locked (incl. Unlocking), keys have a clear pressure point, the wheel is stiff but easy to handle.
On such "little things" you realize quality.
Conclusion: I would buy this product at any time.