The Intel EMGD driver for the gma3600 on Windows XP is what Linux people call a vesa driver. It generates a fake video bios with 16:9 resolutions (the default version), some of which are useful. It does no video decoding using the gma3600 decoder. Streaming flash videos with a "video properties" on the right click show "software acceleration" and "software decoding". You figure what that means. On the same computer running Windows 8 and the super video driver for Windows 7, your streaming flash claims "hardware acceleration" and "hardware decoding" on many, but not all, videos. For some reason, the accelerated driver seems to run much better on Windows 8 than on Windows 7. It uses graphics components that were introduced in Vista to enable Graphics 10, while Windows XP is a Graphics 9 at best system.
You forgot one factor: With the Intel chipset .inf driver, Windows XP runs much faster in general than Windows 7 or Windows 8. That partly compensates for the slowness of the EMGD graphics driver. You can also look for the advanced system properties in the System portion of the XP control panel, under visual effects, and turn off all the visual effects, meaning taking away the system overhead from graphics toys completely, something that also works in Windows 8.
What is really, really irksome is that I also own two gma500 museum pieces, a z510 and a z530, both from Compulab, and there is a gma500 graphics driver that gives video acceleration of the rotating cube variety on both of these computers. The downside is that you have to use the minimal close to 16:9 resolution that best fills your monitor screen, meaning 10-20% wasted screen area. But, the full screen streaming flash on the z510, steaming along at 1.1 gigglehertz, is a sight to behold. So, the question is, if you can get acceleration on the gma500 under Windows XP, why not the gma3600 as well?
Ever since I started asking that question, Intel has been cutting off my downloads.
As for Ubuntu, I tried 12.10 the release version, and it does Windows XP-style EMGD on the gma500 and flat refuses to run in HDMI or DVI modes on the gma3600. Even if you give in and go back to vga on your gma3600 to get Ubuntu to do its thing, all you get out of it is the same pseudo-vesa slow humbug that you get on Windows XP.
I don't know how Microsoft managed to get such an ugly operating system in Windows 8, because ugly best describes it. If Microsoft ever put in something that looked like a Windows XP "classic" style, in place of the modified Windows 95 style they now use, I'd say that swings the deal, and I'll go to Windows 8, hidden "shutdown reset" button and all. And, I maliciously copied the card games from my activated, validatged XP system, and I intend to install them in Windows 8 next chance I get.
