Summary: I think most people realize that Canon makes great products but that they are also VERY overpriced for most people. I needed a flash for general and school use and I very pleased with this item. If you have the %500 plus to pay for a Canon flash, go for it, but if you are like me and many others, less than half that price and you have a Sigma flash. In my opinion, it works just as well as the Canon, but Canon probably doesn't like to hear that.
Pros: Consistent Output, Durable, Easy To Use, Fast Recycling, Lightweight, Powerful Output, Versatile
Summary: I bought this for my digital Sony SLR and it is wonderful especially in low light conditions. The flash rebounds quickly. Just bring extra batteries, after about an hour of solid use it will slow down.
Summary: I bought this flash for my EOS 400D. I didn't have the money for a Canon 530 EX Speedlite, and this item was less pricey than the 430 EX and as powerful as 530 Ex. So, I said: Why not? If what you need is a powerful, fast-recycling, TTL-II flash, this is what you need, for a great price.