the 5600HS and the 3600HS are both rubbish,
I use the 5600HS with no problems. I do agree that many others do have problems, but I'd hardly call the flashes rubbish!
The real problem is that the 7D may not be properly calibrated for the flash and KM will recalibrate your camera for free. Now that KM are getting out of the business, I'm not sure what the situation is.
Why I do not have problems may be just blind luck that my camera was calibrated correctly. I used it for some time with my Maxxum 7 film camera before using it with my 7D. I am not aware of any flash, by any other manufacturer, that is guaranteed to work as well as the 5600HS(D), 3600HS(D) flashes, or to even work at all. Remember that the Minolta cameras have a proprietary shoe.
I don't know what reviews your reading that say the flashes are rubbish. This is not my experience. I have read mostly good reviews. The few that were not good were by people that either did not devote the time to learn how to use the flash with digital, or simply did not know what they were talking about. Here's just one example of a reputable review.http://www.imaging-resource.com/ACCS/56H/56H.HTM
Just my opinion, take it for what it's worth. There are a million experts out there on the INTERNET, all making claims, just like me. :0)