My kids took 2 weeks to get back, however someone else just posted that they got theirs back in the last week or so and it took 5 months.
I had asked, when I applied to have it expedited if possible as we were intending on returning to Canada by November (our hope) of 2010 and that we'd want their proof to land properly at the same time as me (the applicant) and their father (Canadian citizen sponsor). I was shocked when the letter of receipt arrived and then the very next day their cards were in the mail.
GL!