Disclaimer: The show has already been renewed for a second season, so no hand wringing over the ratings is necessary!
Update: (hat tip to James Hibberd) Starz actually reports **lower** numbers, 535K on Starz and another 460,000 on Encore. I'm not sure what's up with the discrepancy in numbers; maybe Starz numbers are Live only rather than Live+SD, or it's something to do with it being longer than an hour either way it's a record for an original scripted premiere on Starz.
Update 2, January 26: The original numbers posted were correct. Starz issued a press release today on Fridays numbers with additional information on the airings over the weekend.
Also as noted in the comments, Spartacus: Blood and Sand had some early online (free) distribution of the premiere, so people had a chance to see it before it aired. Next week's numbers will be more telling.
I don't really have enough historical data for shows on Starz to handicap the premiere of Spartacus: Blood and Sand on Starz that averaged .659 million viewers and a 0.3 adults 18-49. A simulcast on Encore drew an additional .578 million so that's a total of 1.237 million. If that was all on Starz I'd say that was pretty good.
Even just the .659 million might look good after a Crash season two finale that scored a 0.0 adults 18-49 rating and 94,000 viewers!
We'll have to see what the numbers look like when its not simulcast on Encore.
numbers via @TravisYanan