I do not recall the exact date, but I believe it was the week of June 20 went I mailed off the CAIPS (aka GCMS) forms. The letter obviously got caught in the mail strike because the cheque was not cashed for several weeks. The report was received back by email on July 18, which surprised me as I was expecting regular mail. Entire process took approx 4-5 weeks, taking into account mail slow down during strike.
@ sillymemo: DEFINITELY get your CAIPS request submitted right away. I suggest doing a covering letter asking for the results as soon as possible, mentioning the date of the interview. Worth a try.
The sponsor should read the instruction forms very carefully and ONLY check off the electronic file request portion. I read somewhere that requesting anything other than electronic results in a significant delay receiving the response. Also make sure that the applicant signs the Release of Information to Individual form. Include an email address for their response. I also notice there is now a credit card payment form available which I don't believe was there before, as I sent in a cheque. By all means use the credit card option if it means you can fax in the forms and save some time.
As Huron mentioned, the CAIPS report will give you a pretty good snapshot of the status of your application and what the "flags" might be. If an IO is looking for something, it will be mentioned in the notes. Everything in our report was status quo except one note in particular that said "photograph of tattoo described in medical must be obtained for review". So as you can see, the notes will give you a very clear idea of what they want to know.
Once you identify what the embassy is looking for in CAIPS, you will be in a position to clear up any issues at the interview. I think I've read elsewhere on this forum that it is perfectly okay to ask about the outcome of the interview at the end and if there is anything else that needs clarification.
Also, definitely follow Huron's advice and bring to the interview updated relationship proofs since the date you submitted your application - emails, chat/phone records, pictures, facebook screenshots, plane tickets, visit itineraries etc. Just go in as prepared as you can and be completely honest and I'm sure you will do just fine!
This is the link I used to get started on CAIPS:
http://immipedia.ca/Ordering_FOSS_and_CAIPS_notes