The 500 Super most definitely *does* work in the hot shoe of the 7D. I am currently using that combination. I needed to send the flash to Sigma for a firmware update because it was producing extremely inconsistent exposures. I paid for shipping to Sigma, the service was free, as was the return shipping, and it all happened in about one week's time. I was just astounded at how helpful and quick they were about the whole process.
That's helpful - thanks. I have three late-model 500 Supers and they all behave the same on the 7D: in E-TTL mode, direct flash is always hugely overexposed; bounce flash is better exposed but still erratic. Manual mode works fine. In master mode, it doesn't flash in any circumstances. With a prime lens attached, the flash's zoom head often hunts between settings, e.g. between 85mm and 105mm if a 100mm lens is attached. With a zoom lens (e.g. 24-105mm) attached, the flash's zoom head cycles several times from widest to longest settings before stopping at a random setting. In contrast, all three flashes work perfectly in my 5DII's hot shoe!
I'd like to see if Sigma UK can update the firmware on my units. It would be very helpful for me first to know how long ago you got your update, and also which version of the flash you have. The three 500 DG Super versions respectively had the following inscriptions above the LCD :
ELECTRONIC FLASH EF-500 DG SUPER EO
EF-500 DG SUPER EO - ETTL
EF-500 DG SUPER EO - ETTL II
Thanks for any help you can give.