This is the first proper flash I bought for my EOS 40D and have been blown away by the quality of the images it lets me make. My previous experiences with flashguns have been pretty hopeless, totaly nuked out highlights and black backgrounds.
I wasn't expecting much from this but the e-ttl metering really does a fantastic job of determining how much flash to give each image. I took a few photos of my daughter when she was wearing a bright white jumper and thought it would be totaly overexposed. No, they turned out fine, bright but not blown out.
Anyone in the know about flash knows that on camera flash is the worst place for a flash to be positioned. However, the quality of light given by this flash really does look good. Sure, I prefer to bounce the flash or get it off camera but in a pinch it can be left on camera, set to auto and pointed right at the subject.
The feature set is pretty formidable, hi-speed sync at all shutter speeds! This lets me take flash photos at 1/8000th sec which is cool. The manual controls are good, with power reduction down to 1/64th. There is a modelling light, 2nd curtain sync, focussing beam and slave functions.
The big drawback with Canon SLR's is that the flash cannot be remotely fired by the camera unless you purchase the Speedlite ST-E2, which is basically a hotshoe mounted infrared trigger. Sadly this item is hugely overpriced at about 150 pounds. This immediately limits the creative aspects this flash offers unless you get into radio triggers. The cheap ones from ebay do the trick but unfortunately the e-ttl ability is lost.
This is a hugely disappointing move by Canon, how hard would it be to incorporate an infra-red trigger into the SLR's? Nikon and Olympus do it.
However, once this difficulty has been overcome the flash comes into its own. The look from bounced flash is very natural and evenly light. I have started bounce flashing from walls and interior doors and the effect is subtle and really nice looking.
In summary, if you have any interest in using flash forget the built in flash on your camera, it is not going to take you too far. Try this flash and your photographic opportunities will be expanded exponentially.
A fantastic flash.