Got my PS3 through the Sony Bravia promotion. Had a dodgy PS3 with the loud fan noise issue. Sent it back to Sony for replacement, but didn't get registered post. I called up Sony several times to see if they had received it, but they didn't receive the PS3.
Up until around 2.5 weeks with no sign of PS3 being received by Sony, they tell me to fax in the receipt of the post office. So I faxed it in, and then the next day they sent me an email saying they've received the PS3 (which they probably lost it in the first place). 1.5 weeks later (Today) I receive my 2nd PS3. So in total it took me 4 weeks to get a replacement. If you include the time waiting for the first PS3 to come from the promotion, that was about 5 weeks. So took me around 9 weeks in total to get a good PS3, for now .....
Hope you got registered post, or else it's going to take ages as they'll probably say they haven't received the PS3, and to wait another week etc ...
Good luck !!!