I had sent off my Xbox for repair on Monday afternoon, and got a nice surprise when I got back from work today:

The letter:
Dear Xbox 360 Enthusiast:
Thank you for being a part of the Microsoft Xbox 360 community. We have repaired your Xbox Video Game System per the terms of the Xbox warranty and are returning the system to you so that you can continue to enjoy the exciting video game experience that Xbox offers.
If you have any questions, please contact Customer Support on 0508 555 092; TTY users call 0508 555 594. (do we have 0508 numbers in Australia?)
Please accept our apologies for the inconvenience you have experienced by having to send your Xbox 360 in for repair.
It is our goal to provide you with the best gaming and entertainment experience possible, and hope to regain your trust, satisfaction and loyalty.
Please accept this complimentary one month Xbox Live membership card to (sic) as a gesture of our appreciation of you.
Thank you for your continued support of Microsoft Products and Services.
Sincerely,
Xbox 360 Customer Support
Well…it’s nice to be "appreciated".
But anyway, it’s back! Big ups for MS on the speedy repair and return.
The console has basically reset most of my factory settings (like the resolution, the IP configuration for Xbox Live, the time, the location etc.), and it sounds a little bit noisier. Before it was a whooshing sound with the fans; now it’s an annoying whir, not unlike a heavily muffled fridge compressor. I won’t be hearing it over my speakers, but at least something was changed to make it work. Who knows - maybe they wrapped it in a warm towel for me and sent it back.
Now…to pick up my copy of Mass Effect.