Hi,
Dont know about the auto option on the sport IS250, but with regards to the black paint, I have had 4 IS cars, 3 of them black and one of them Kodiak Sky.
All cars were bought brand new and were Superguarded prior to collection, the 2 Black IS200 always looked absolutely superb after they had been washed - even with 40,000 miles on them - although my IS200 in Kodiak Sky (metallic) never seemed to look as good. So I would say order black, save £550 and get it superguarded by the dealer.
The only thing that lets the Lexus range down are the quality of the Alloy Wheels, I cannot remember how many sets I have had replaced but its more than 5. I just hope they have got it right with the IS250.
Hope this helps, by the way add gold badges with the black and everyone admires the car and comments.