I've been driving mine in E, T, and S modes for the breakin and definitely feel a difference between the three, especially in power. But at about 700km (150km before the rev limitier warning bars came off) I noticed a large increase in power coming on. I'd hit 4000rpm MUCH faster and have to shift. I recall taking the car out at the beginning in S mode and trying to get the back end to break loose to see how the electronics caught it... I could barely get it to slide in 2nd or 3rd gears. Now when I put down power in a turn the back immediately comes loose and slides around until the electronics cut power and straighten it out. I can actually get two power slides in one corner by staying on it hard til the electronics catch the slide mid corner and when they give me the power back I can get another slide before I have to straighten out.
That power wasn't there the first 500km, I'm sure of it. So after about 150km of this, I did the break-in procedure recommended by some engine builders in here, one summary is: New Engine Break-in Procedure
Essentially, it involves taking out the 'too slippery' synthetic and replacing it with high quality, low viscosity oil, not synthetic (I used Royal Purple break-in oil). For the 500km that this oil is in, you build up how hard you drive the car (though staying below 4500rpm since you don't want really hot cylinders). Swap out the break-in oil for the good Mobil 1 synthetic and away you go. Read the link if you want the detailed engineering reasoning...
And as always, it's your car... make your own choices, this is just a description of what I did.