Let me say this, when this flash is doing what it does best, the results are fantastic. Thanks to the rather funky auto focus assist beam that comes out the front, this will focus in complete darkness. The white balance information passed to a compatible camera (all the new EOS D models) makes for well balanced shots, some of which it's hard to believe that a flash was used in the first place. Cycle times with new batteries are impressive
There are a few niggles though:
The rotating head swivels 180' in one direction but only 90' in the other. If you're into bouncing your flash, there are situations in which this can be limiting. Getting round it involves using the camera upside down, which is rarely practical. Surely this would have been an easy thing to implement.
The controls on the back are somewhat fiddly. Most of the time, you won't need to alter the controls off auto, but when you do, the left and right buttons are hard to press in because of the surrounding material. This is one place where the 580 really puts itself above this model; the rotating dial is far more user friendly.
Battery life isn't amazing. If you're using the flash on high power for an extended period, make sure you've got a spare set or are using lithium AAs. Lithiums really do take the worry out that you're going to run out of juice, at a price of course.
I've highlighted the negatives more here, but don't get me wrong, I am very glad I spent £160 on one of these new and I sing its praises when I get the shots I want. I've been amazed by the distance it will cover with my 200mm lens.
Further to the flash, I'd recommend the purchase of two accessories. In order, I'd suggest: a StoFen omni-bounce. For near work, especially when combined with bouncing, these really soften up the light for more flattering shots, especially portraits
Secondly, the off-camera shoe cord V3. This lets you bounce flash from wherever you like and gives that wonderful off-axis lighting effect. One thing to consider with it though, the Auto-Focus assist beam is a lot harder to aim manually than you think it's going to be holding it a foot above your head!
All in all, a great product that isn't beaten by its cheaper imitations.