The page D4 of the Personal Journal section of Tues Wall St Journal has an article about the first two '2 mode Hybrid Drive' vehicles shown to reporters: the GM Tahoe and Yukon.

This drive combines twin dc motors inside the automatic transmission with a 300 volt battery pack and electric power steering thrown in for weight reduction. To partially offset the weight of the battery and motors the vehicles have aluminum roofs, hoods, bumpers and tailgates.

Since a big advantage of hybrid drive is to re-capture some of the energy normally lost in braking, and since 60% of the braking is done by the front wheels, I am not sure if the system will capture much of this unless the braking is very gentle engine braking.

Daimler Chrysler will be building vehicles with this trans with twin internal motors and battery packs too.

The MPG in the EPA test is claimed to increase over 20%

 

This hybrid system will provide a low speed and high speed electric motor to assist the engine in driving the vehicle through the transmission. The battery packs get recharged from the energy created under braking. This is not like Toyota or Honda that have a 2 mode hybrid either electric motors or engine. This combines the both at the same time, all the time. Reports indicate that it will increase economy 25% and the first chrysler product to get this will be the Durango.
The way you wrote your post you made it sound like it will only benefit the vehicle under braking. It will benefit most under acceleration and towing. Combine this with the MDS and we should have some decent economy numbers. But, the way I see it it's just another reason for the oil companies to increase fuel prices.