I'm thinking about using it instead of the TLC5940 (needs too many pins, and PWM signal).
When I saw this huge 8x8 rgb matrix led board at sparkfun.com, I just wanted to build one that supports true rgb colors, nut just the 8 colors or so that are predefined with their serial module. Speaking of which, theirs is common cathode so it won't work with the 6966 directly. I know the led manufacturer also makes common anode ones, but I just could not find a source for these in europe.
Just looked at the data sheet and functionally it would appear to be just a 10 output version of the 16 output TLC5940. I am not sure why you say this needs too many PWM signals it doesn't need any it produces them.
The MAX6966 would be amenable to the same tricks as the TLC5940 when it comes to driving a matrix. That is you would have to multiplex it and change the PWM values before each refresh scan. My view on the RGB 8X8 matrix is that you are probably best doing it all in software (bar the odd driver) and dedicating an Arduino to do it. Any extra hardware support buys you some more process cycles if you can squeeze you actual application into them.
Regarding the pins, the 5940's manual has made me believe it needs VPRG,GSCLK and BLANK lines in addition to just the 3 spi lines.
Just like here: Arduino Playground - TLC5940
The MAX chip seems to run with just clk, latch and data. So I would not have to mess with timer irqs to generate the pwm for GSCLK.
The 2 drawbacks I could see are the MAX's form factor, which makes it a no go for hole matrix boards, and that it just delivers 20mA per channel.
And of course I can't get hold of the led matrix without the wretched import customs crap.