I loaded the code into my Duemilanove and connected it up to my Cat4101's, Looks good so far. I made some changes to the code to run the leds at max (1023) all day,and set the night time level to a minimum (20) for moon lighting at night. I think a pwm value of 20 works out to be a hair less than 2%. I should know by 10pm whether or not the leds will continue to run at such a low setting.
I did notice that there's something amiss with the time display in the serial monitor. The time displayed is 1 hour less than the correct time on my PC. Any idea what's causing that? Must be something to do with the DS1307 and daylight savings time?