I arrived in DEN last month and the immigration took less than ten minutes. I flew in C but passed most F pax on the way to the immigration both. Then it took quite a while to wait for the luggage, but I had worse times for that before as well.
I can top that experience: Last two arrivals in DEN immigration took less than 2 minutes.
Being first off the plane does help of course.
I was in the RCC West in under 30 minutes after touchdown with LH!
Fantastic!
I chose my US flight based on immigration, if I have to connect anyway. NY it's the BA1 from LCY (immigration at SNN), the West is usually DEN (LH). I also like the late BA flight into SEA, as there seem to be no int'l arrivals then.
I try to avoid LAX, except when arriving from Asia.