No personal experience with the flash, so please accept that this is my educated opinion.
If you notice in most reviews, the key words are ok for the price. It is definitely built to a price, no where near the build quality of a Canon flash, and thus will the Bower fail on you at a very inopportune time or not? With anything of low quality build, you just never really know. I certainly would not want to rely on it for any kind of extremely important shoot such as a wedding.
As to the specs, the flash only has a guide number of 112. Certainly better than a pop up, but a long way from a Canon 580 with almost 200. When you use the flash with a diffuser, (which you should do with any flash), then that lower power will really make itself known.
Also, the flash has no variable power. This means you have no manual control of it. You are forced to accept whatever the flash deems to be an appropriate exposure. ETTL is good, but not always perfect. There are times when you MUST have full control of the flash power to get the lighting you need / desire.
Bottom line, you can't expect a $50 flash to equal the near $500 Canon 580EX II, (though I also agree that the price of the Canon flash is absurdly high).
I suggest you study some other flashes, such as made by Sigma or Vivitar or Sunpak that are also dedicated flash units made to work with the ETTL function of the Canon. They will cost more than the Bowers, but will be less than the Canon, and a better unit than the Bowers.
steve