I haven't seen any demo info yet, but the premiere of Torchwood: Miracle Day was on par with the premiere of Camelot. The good news is that Camelot was Starz' highest-rated original series premiere to date. The bad news is Camelot was, you know, canceled. It's the future numbers that will tell the tale of how Starz feels about Torchwood. All the caveats of "it doesn't include On Demand or Internet viewing" apply, but they applied with Camelot as well, and neither Camelot or Torchwood: Miracle Day was available immediately on Netflix.
Here's the info via Starz:
“Torchwood: Miracle Day’s” post-holiday weekend premiere on July 8 delivered a combined Friday night audience of 1.51 million viewers P2+; 819K viewers for Friday at 10PM ET/PT (1.9 Live + SD HH ) and 687K for 11pm ET/PT (1.4 Live + SD HH Rating).
Total weekend viewership (Friday airings + Sunday 10PM ET/PT and 1AM ET/PT airings) was 2 million viewers P2+, Live + SD (1.96M).
The performance of “Torchwood: Miracle Day” was at parity with the network’s April debut of “Camelot” (1.57M viewers Friday night/2.087 weekend million – both P2+, Live +SD), Starz highest-rated original series premiere to date.