I did it, for a couple of reasons:
1. Fuel economy. I was hoping for a big increase, but I'm getting just about 1 mpg more... Or that could be me being light footed with the winter tires.
2. Tire preservation - I bought expensive michelin ice X3's I want them to last, Limiting power through limited boost and torque is nice.
3. Money savings - Economy mode allows for use of regular 87 AKI fuel. I am saving 40 cents a gallon vs premium. even if improved MPG is a wash I save massively at the pump price.
The car is still pretty fast even in eco mode. Faster than my fiance's 06 civic EX. That's good enough for me, as we have driven that 70,000 miles around the USA and Canada, no NEED for more power or speed.
I say do it! and enjoy the $$$ savings, so you can blow it out the turbo come summer!