I finally got around to watching the first part last night. I too was slightly underwhelmed, but it was definitely good enough for me to keep watching. Have to say I found the criminal/Eccleston bits far more interesting than the police side of things, although the reveal at the end was interesting.
I also enjoyed Who spotting. Ninth Doctor, check, woman out of Midnight, check, Rani's dad, check...
It appears to be 7 episodes long so I'm assuming there'll be a lot of twists and turns on the way.
The guy playing the psycho nephew was really odd...