In my case, I have a B1 on my current passport and I wont have enough time to have my passport surrendered. Also, I am just transiting through US to Mexico.
I am planning to submit the application once I get my Canadian passport and take a copy to show to the immigration officer that its in process.
Fatefully
, this is my first travel after my NEXUS application got conditionally approved on my current passport. Not sure how that's gonna go. The Canadian interview is scheduled in November, however the US one, I believe happens at the post of entry.