It's new to the 2012 Evos. On the other forum under Canada, we have a member who works at a dealership and has already put in an order for the 2012's scheduled for November. In Canada anyways, we'll get:

Auxilary audio input deleted (GSR and MR)
Brake Overide System added (GSR and MR)
New pattern on interior decoration panel added (GSR only)
Phantom black decoration panel is replaced by Gloss black decoration panel (MR only)
"ECO" mode / Gear Shift mode indicator added (GSR and MR)
Soft pad trim on inner door panel centre and upper portion added (GSR and MR)

The Brake Overide System (BOS):
Mitsubishi vehicles feature drive-by-wire throttle technology that eliminates the mechanical connection between the gas pedal and the engine. Consequently, when a driver in a panic situation inadvertently steps on the throttle and the brakes at the same time, the system disables the throttle. The net result are vehicles that stop in a safe and controlled fashion.

If it works as intended, that's great, but there's the fear we can't left foot brake nor heel toe revmatch downshift.

 

I seriously doubt it will disable rev-matching and left foot braking. Perhaps you'll have to disable ASC to get it that way, but mitsubishi is well aware we drive the Evos like that. On the 8's and 9's they engineered the pedals to be with-in a perfect distance of each other to make heel-toe easier.

The X was developed for Gruppe-N down to the smallest spec. I'd be quite impossible to race such a machine if such a thing couldn't be disabled. I wouldn't worry too much about that.

 

I test drove 4-door 2011 STI less than an hour prior to test driving my 2011 MR. I'm sure on paper the STI comes close, but everything about it felt less connected to the road than the Evo X. It felt softer, cornered with more roll, and I hated the way the clutch felt. My prior car was a 2009 NISMO 370Z which has a sharp quick clutch engagement and the STI just felt squishy. The seats in the STI also felt too short for me. The back of my head was just at the top edge of the headrest (I'm 6') and in the Evo X it cups the top of my head more.

The nice things the STI has that my base MR doesn't are a cold weather package (heated seats + heated side mirrors + heated element in the windshield), leather trimmed seats, rear fold down seats and a larger trunk. There are also built-in slots for a roof rack whereas on the Evo X we have to clip them into the roof gutter.

Overall I would say the STI is more practical, which is why I looked at it in the first place. Driving it however didn't give me a rewarding experience. The Evo X did.