Demo ratings were still solid this week despite slipping total viewership. I'd speculate that the competition from American Idol is hurting them.
09/17: 7.700 million, 3.7 18-49 rating (series premiere)
09/24: 5.400 million, 2.8 18-49 rating
10/01: 5.800 million, 2.9 18-49 rating
10/08: 5.100 million, 2.0 18-49 rating (move to 8pm)
10/15: 5.100 million, 2.0 18-49 rating
10/22: 5.200 million, 1.9 18-49 rating
10/29: 5.500 million, 2.1 18-49 rating
11/05: 5.600 million, 2.3 18-49 rating
11/12: 5.100 million, 2.1 18-49 rating
11/19: 5.100 million, 2.0 18-49 rating
12/03: 5.400 million, 2.2 18-49 rating
12/10: 6.000 million, 2.3 18-49 rating
01/14: 5.418 million, 2.3 18-49 rating
01/21: 4.733 million, 2.1 18-49 rating
02/04: 5.220 million, 2.2 18-49 rating
02/11: 5.250 million, 2.3 18-49 rating
03/04: 5.056 million, 2.3 18-49 rating
source