For K-3 visa holders how is POE?

what do they ask and how long is the procedure?

For me it was very easy- I had a very early flight and there was no line at US Customs (In Canada- you go through US Customs before getting on the plane) When I was called to the kiosk- I said "I need my K3 activated." The guy was very nice and said "This is a good day for you." He took my passport and package and brought me into the back and handed my stuff to someone else. I sat in the waiting room for about 10 minutes and he called me up and everything was done- he gave me my passport with the I 94 stapled in it- he reminded me that I would have to file for Adjustment of Status after I get back to the US . I grabbed my luggage and proceeded to security and waited to get on the plane.

My husband said his POE was not hard at all. The officers were very friendly and took the brown envelope from him that he got from the embassy and was told to give it to the POE officer and not to open it. They didn't even ask him for his xray they took his passport and stapled the I-94 inside.
It did take him like 3 hours to get through customs though not because they were giving him a hard time though I think it's because he brought all kind of food from Nigeria that held up the process.

Ours took about 10 minutes and we were bringing my wife's dog and cat too! Completely painless...I was happily surprised!

It was the biggest pain of the whole trip for us. We were there for an hour and a half because my daughter's K4 Visa had no alien number with it. I think they just made up a number just to get us out of there before the next international plane arrived. I'm using the A number they gave me at POE so I'll see if it's any good when I send in the AOS paperwork