My husband landed today via the Douglas/Peach Arch crossing! We're very relieved that it's all over now.
We encountered a minor glitch when we (or rather I) decided that because the line into the US was kind of long, maybe we could just turn around and go back to Canada (there was a spot where you could turn around and return via the Canadian border. No dice, the border guard made us go back to the US and 'get the flagpole paper' When we got to the US border officer, he was super nice and explained he couldn't deny entry to a US citizen (my husband) so the best he could do was send us into secondary and they could stamp his passport with today's date, but that was it. He was also nice enough to send us to a line that was very short rather than the main lineup (which was very long!). The officer inside was also helpful -- I wish I could have said the same about the Canadian border officers. The second time we went through the Canadian border, the border officer didn't seem to even care he'd had his passport stamped. (Time spent in lineups - 1 hour.)
As luck would have it, we got the same officer who originally told us to 'go back and get the flagpole paper' for my husband's landing. She was a bit nicer once we were inside, but no 'Welcome to Canada' once everything was signed and completed - she was all business. She did mention the important things (go to Service Canada to get your SIN, your PR card will arrive in 5-6 weeks, you must be in Canada 2 out of 5 years to maintain your PR, although any time spent abroad with your wife counts). We had filled out the B4A form to import his car later, and she informed us this was the wrong form and she would fill out the correct form for us.
Anyway, we're glad the process is now over -- thank you to all the helpful people on this forum! I wish you all the best.