It looks like, quite possibly, Renault been quite brave indeed.
Blown rear diffusers or rear wings have been on and off F1 cars for several years, the simple view is that you point the exhaust pipe of the engine at a sensitive areo area of the car, either to increase airflow in one area or to decrease airflow in another, and one supercomputer of advanced math later, you have increased downforce when you need it...just enough to make that difference in a highly completive race series.
We can't easily recall other areas of a race car getting the exhaust-blown treatment, but pictures seem to indicate the RB31's exhausts actually travel forward and exit toward the front of the sidepod, perhaps enabling better airflow over the floor right around the midsection of the car. This is particularly neat, because, should it actually work, they'd be getting additional downforce around the midsection of the car, which should give even more flexibility than just more downforce at the rear as with the 2010 cars using that setup. Which could lead to a significant advantage.
However, some serious challenges with heat come to mind - not only with running the exhaust pipe forward near the driver, but KERS returns to F1 this year, and that means another component in the car that needs extra cooling. And the tradeoff between cooling and areo efficiency is a very tight balance as well.
So will this thing work?
I'm reminded of another clean sheet of paper design released in June 2007 by a small computer company that had just 5% share of its market at the time. The main press thought they just might be on to something with their radical approach...some neat new features but glaringly lacking in others. Brave engineers too, and things have worked out quite well for them.
The Renault R31 needs to be ready to race March 11th. I have a feeling we'll know pretty quickly thereafter if the old John Player slogan 'Something Very Special' ends up referring to the R31's pace, or its ability to light up and burn at one end.