Yes, I installed Win7 as well. You can install the graphics drivers from the download centre, there is one with Win7 in the file name, but the drivers are unsigned so you need to reboot with F8 and select the unsigned drivers option. This then at least gives you full screen and 1080p for media center. However, the HDMI audio definitely doesn't work until we get new BIOS and/or drivers.
I'm using an SSD and isn't booting with UEFI, I am assuming this is a Win7 thing.
I will cope for a few weeks rather than fork out for Win8.