The significance of AOR is not, of course, that you know they received your documents. Your courier and the fact that they charged your card or cashed your draft will tell you this. It's that your application has passed the CIC stage of completeness check, and then eligibility review.
Currently after CC/DD cashed you are completely in the dark until you get your AOR with file number. After that you can check the status of your application online, so at least have some glimmer of hope each Tuesday that they have updated it.
I suspect that they spent a large amount of time over the summer on student visas, coupled with the unusually large intake of applications during May and June, hence the silence on AORs until now. The completeness check leading to encashment is probably a very quick process, whereas with the eligibility review they have to check all the info on your forms (and for post-June-26 candidates they will probably go through all your educational documents and work experience etc) - and calculate how many points they believe you have accured.
This is why we are all very eager for some AORs to start filtering through!
Wayne.
