The reason behind buying the 2nd ACD would be more for when I buy my Mac Pro in Jan/Feb '09 because at that point, I would want 2 ACD's.
Good choice. I am eyeballing dual 23"/24" ACDs with the purchase of my Nehalem Mac Pro to replace my aging G5. I could grab two of them now, but sense I don't need them know I will wait for that hopefully updated ACDs with H-IPS panels and more FW400/FW800 ports for around $1000.