Note: This is only my experience. I don't know how it differs from others.
My husband was a Canadian, I am American.
I came to Canada on May 26, 2009 to visit my husband for the summer (we were only seeing each other then). While I was here, with my daughter with me, my husband I got married. When we first entered Canada, we were both given stamps in our passports rather then a TRV. I believe this is customary. Our stamps indicated we were allowed to remain for 6 months. In August, we went to a land crossing and got a student visa for my daughter so that she could remain in Canada and go to school. After that, I applied for an extension of my temporary visitor status (based on my passport stamp), and was approved until August 2010, which is what I asked for, to make it match my daughter's student visa.
We got our medicals done in Calgary, for an outland application (make sure the medical folks use the right forms if you are doing outland as opposed to inland), and we paid our fees, and finally got our package submitted in March.
In late March I had to take an emergency trip back to the States. When I returned, I had my paperwork with me at the land crossing (it was cheaper/easier for me to fly to montana then drive across the border). The immigration agent appreciated that I was very well prepared and it was painless, even though I had been very nervous about this. I brought:
A. Marriage license
B. Receipt of payment of application fees
C. Printout of tracking page showing my package had been received at CIC-M.
D. Passport (obviously) with TRV in the back.
Luckily, I also had an itinerary for another trip I am making this summer, so I brought that as well.
The immigration officer told me to come on in, and reminded me that I had to leave Canada or apply for a visitor extension for myself and my daughter by the end of August. He also mentioned he could see that our application was in the system, (this was before we had heard anything yet), and wished us the best of luck. While I know that some folks have had some very unfortunate experiences, I have to say that almost all of the stress of immigration so far has been self-generated. The actual experiences I've had at the border have all gone very smoothly, even though I was very nervous about them ahead of time.
Hope this helps someone out there -- I know I've gotten lots of reassurance and information about how to be prepared for crossing the border here from others.