For me it took 2 weeks from the date they receive it and the date they started processing. Timeline: received Jan 14 2013, started processing Jan 27 2013
You can check the status online, that is how I found out they started processing the application. What it really means is that they have opened your package.
Count around 100 days and you should get your new card after that. I don't think they communicate with you unless to tell you that the new PR card is ready OR if there is an issue
Hope it helps