Charlamag: I agree with justina. I too applied inland and needed to wait to receive my PR card before they would give me a SIN number.
Only a few local offices hold a Service Canada in the same building and give the SIN number to inland applicants without the need of a PR card.
It even states on this page on the Service Canada website that PR card is the only thing they will accept for inland applicants (of course except for the scatter few local offices). Here it is:
http://www.servicecanada.gc.ca/eng/sin/apply/proof.shtml
And it states the following: "Permanent Resident Card issued by Citizenship and Immigration Canada.
This is the only acceptable document if your claim was processed in Canada." Claim processed in Canada = inland process.
Anyway, as long as this doesn't cause conflict in the landing process (which I am confident it won't) and doesn't delay getting a SIN number like it does for some inland applicants, then I believe this will be great. Plus as Baloo stated, no worry of losing your passport in the mail. When will this come into effect rjessome?