Dana White announces the news on his Twitter account:
danawhiteufcTuf 10 premier did 4.1 million viewers last nite!!!! Thank you all very much. You are the best fans in sports!!!
Some more information from F4WOnline.com:
Last night's show did a 2.9 rating with 4.1 million viewers, making it not only the most-watched episode in history (old record was 2.8 million viewers for the final episode of season 3), but also was the highest-rated debut for an original series in Spike history.
I don't think it can be stated how incredible this number is. To beat the previous best by 1.3 million viewers is something else. We'll see if the number will nosedive or not, but it's safe to say the UFC's gamble with Kimbo Slice has paid off.