Poor image quality on Thinkpad T60 notebook WXSGA+ w/ Intel Corporation Mobile 945GM

[Gregory Maxwell]

I purchased a new Lenovo T60 with a (1680x1050) WXSGA+ display
(LTN154P2-L05 is the panel) driven by

(--) PCI:*(0:2:0) Intel Corporation Mobile 945GM/GMS/940GML Express Integrated G
raphics Controller rev 3, Mem @ 0xee100000/19, 0xd0000000/28, 0xee200000/18, I/O
 @ 0x1800/3

I chose the Intel graphics rather than the 'enhanced' ATI offering
because I do not care about gaming and I wanted hardware supported by
open source drivers.

I am using FC6 (for x86_64) with updates applied... rpm claims my I am
using xorg-x11-drv-i810-1.6.5-10.fc6

However, I am disappointed with the image quality of continuous tone
images.  Even in 24 bit mode the image only appears to be 6bits per
color component (and changing to 16bpp doesn't appear to change the
image at all), but worse there is a faint horizontal banding in the
display similar to what I remember seeing on old interlaced displays
with low refresh rates. This came as a shock to me, the quality of my
prior thinkpad displays has been great.

I'm pretty sure the driver thinks this card is in 24 bit mode, since
I'm getting these log entries.

(**) I810(0): Depth 24, (--) framebuffer bpp 32
(==) I810(0): RGB weight 888

I've tried toggling the "Dac6Bit" option as well as upping the video
ram setting. I've also tried switching to 16 bit mode as mentioned
above.

I don't have an alternative operating system to boot on, so I'm unsure
if this poor quality is just a limitation of the hardware or some
shortcoming of the driver (so input from anyone else with the same
hardware under another OS would be useful).   ... I'd like to know if
it's the hardware so that I can try to return the system... although
I'm not sure what I'd buy instead: I really like all other aspects of
this system.. and I am not willing to run a binary only driver, I'd
rather take the poor image quality.

Any advice would be greatly appreciated, and I'm perfectly willing to
compile and run instrumented code.. or perform whatever tests you
like.

I was directed here by the folks on the freenode #xorg channel, if
I've asked in the wrong place... please give me a polite shove in the
right general direction and I'll be out of your way in no time.

Thanks for your time.