Have had some time to test the new ML Alpha release for the 7D and can happily report that everything works fine, a bit slower, plus the camera heated-up (around the LV button and AF-Lock area just above the joystick controller), so much so that after about an hour's use, I was a bit concerned so turned off the camera.
I plugged the 7D into a 25-inch monitor using the mini-HDMI out cable and tested every possible menu item for both video shooting and still photography. They ALL work GREAT! What is really surprising is the CPU usage of the 7D - seems to be operating at 90% to 95% most of the time when focusing or shooting video (indoors) between ISO 800 to 1600.
For those 7D owners that are interested in the ML firmware upgrade, I'd say try it for yourself. The only drawback is that the 3-inch LCD screen on the 7D is too small to really appreciate the additional functionality and information, unless of course you're shooting video and using an external monitor, then it is a big step up.
I really like the focusing %, the zebras (I set the underexposure to 3% and the overexposure to 84% in the sub-menu, because it defaults to 0% and 99% respectively, so anything white will appear overexposed), the real-time histogram is great and you get separate dots for R, G, or B so you can adjust shutter speed and aperture on-the-fly and see where you begin to lose the highlights etc. The horizontal electronic axis is seamless and appears to be more intuitive that the Canon dual-axis one (you can see behind and it doesn't get in the way).
And all of these are just for starters. Have to say it though, most are aimed at videographers.