In the "How to Keep your Volkswagen Alive a Manual of Step by Step Prodecedures for the Complete Idiot" it specifically mentions this topic.

Even with auto tranny expensive mercedes, the idea still applies.

Brakes are WAY cheaper than almost ANY component of the drive train system.

My concern would not be with the transmission so much as the drivesaft rubber joints.

Those thing do not take abuse so well. (and they are SPENDY!)

I eat brakes up fast but ya know...I drive really fast and brakes a cheap and easy to replace I figure its not worth shocking my engine at every stop sign.

Now when it comes to the occasional downshift for a hill or 100mph-0mph stop...then I will usually try to give the brakes a break rather than use them for all the load. After you drive a car with crap brakes you know when you are abusing them and just merely using them