Hi Shashi,
I finished my landing last Saturday and entered US on AVR after spending around half an hour inside Canada. On the Canada side, the officer on the booth checked my immigrant visa and COPR and gave me a yellow slip and asked me to go to the immigration building. There was no one but agent inside the building so no wait time to process my COPR. Once that was done, I turned around my car and entered US.
On the US side, the officer checked my expired F1 visa, valid I-20 and I-94 and also my unexpired EAD card, asked me where I live, where I studied, what I studied and asked me when was the last time I went to India and when I came back to US and then he let me. I did not have to step out of the car on the US side.
It was a very smooth experience overall.