According to Fight Ticker, Strikeforce drew 364,000 viewers for their first Showtime show on Saturday night:
Avg. viewers: 364,000 Avg. rating: 0.64
Males 18-34 viewers: 100,000 Males 18-34 rating: 1.53
Males 18-49 viewers: 168,000 Males 18-49 rating: 1.28
These are pretty good numbers. There are a number of meaningful comparisons to make here. Below I list past Showtime MMA programs and thier viewership numbers, courtesy of Dave Meltzer at Figure Four Online and MMA Payout:
Kimbo Slice vs. Tank Abbott: 511,000 viewers
Frank Shamrock vs. Phil Baroni: 365,000 viewers
EliteXC Return of the King: 350,000 viewers
Frank Shamrock vs. Cung Le: less than 300,000.
Overall the recent show appears to have done the third highest MMA rating in Showtime history. The number isn't some kind of stunning success, but it is very good. They didn't have a pre-fight special, but still drew a nice audience.