Oh. Well. From my personal pov:
More than a year ago my old Sapphire HD 3870 (Ultimate ed.) was doing during idle periods
about 75 W (whole computer w. 4850e CPU, HDDs, some USB, PCI cards, ... without screen) "from the wall" with (Gentoo) Linux (dunno which kernel) and fglrx.
80 W in Windows (NT 5.1 aka XP) w. Catalyst
85 W free driver stack (not sure if I had KMS at that time, otherwise same Gentoo installation).
So fglrx in Linux was best, 5 W more in Windows, and another 5W more with free drivers. Not super shiny for the free drivers and visible difference but not screaming bad.
With just the onboard HD3300 the difference was less visible (all around 45-50W or something).
I should really measure stuff today again with my HD 5670, again Sapphire. But iirc. the difference last time I tried was not so much. Same mainboard still with a mediocre DSDT and stuff (MSFT compiled).
So I think it actually got better, but to be exact I would have to find my old 3870 and compare again. (The 6xxx series was out already but I chose the 5xxx series since I knew it was better supported at that time.)
But then, I have a dedicated card, from a vendor that normally sticks close to the AMD-ATI reference design. (And with my poor user-only-knowledge) I guess a lot of problems might also come from vendors doing their own tweaks and modifications, especially on laptops. Then any default mechanisms might not get a good grip so you need a lot of quirks in the drivers.
At least here on Phoronix I rarely see anybody complain about missing OpenCL features but daily requests about power management and video accelearation issues (UVD/shaders). So maybe the AMD-ATI devs reading here should note to their superiors that these things and some 3d performance improvements seem to be a really pressing point among users. To give that more priority.
About the lack of coders: I wish I could code. Then I'd like to spend some time on that stuff. But I decided to study chemistry instead of informatics / coding. And now I am partially even working on weekends on my PhD stuff, revising student's lab protocols and revising proposals for scholarships from foreign students and whatsnot. :/
So no chances for me to get into coding rand contributing.
All I can do is to spend some beer, cola or Mate tea for devs to keep them in a good mood. ;-)
Stop TCPA, stupid software patents and corrupt politicians!