I watch almost only for the Stig. My kids will drop anything they are doing to watch him do a lap and are totally amazed that noone "knows" who he is.
Much of it can be tedious: any Captain Slow bit, or UK personlities, unknown to US audiences, driving a POS around the track.
I also cant imagine anyone watching for unbiased car reviews, who the hell will be buying a Koenigsegg, Gumpert, or Veyron anytime soon? Its all schtick and pure transportaion based entertainment.
You have to admit watching Sabine try to break 10min around the Ring in a van was pretty good and my kids also loved this one: