the 2007 cars had ASR, but it had very similar traction control to what the Marketing men have now decided to label as "Electronic Q2".
ASR had two stages.
1) as you describe, cut the power when you are applying way too much power.
2) When just one wheel is spinning , apply the brake to that individual wheel. Practically all modern traction control systems do this.
So whats the difference with electronic Q2 as compared to ASR?
Mainly marketing I suspect, plus some improvements based on refinement over time I'm sure.
The "old ASR" was useful for "normal" driving on roads when you weren't pushing on particulary (which would be 99% of the time).
On track though you really just had to turn it off since it
a) Was only partially effective in restraining unloaded wheelspin,
once you had over a certain amount it resorted to backing off the throttle anyway - since it could tell it would just be cooking the brakes.
b) ..was quite slow in returning the power to match the available grip while cornering compared to a vaguely keen driver, especially if any transient bumps were encountered - which didn't actually really require the throttle being backed off severely.
c) ASR also didn't do much for the brakes since it was reducing the amount of cooling time they had available between corners.
In the wet it was just plain useless for track use, you came to a standstill (relative to other cars) when you hit a modest puddle.
I have read a number of contributions to the forum regarding the system and although I am certainly not defending its introduction in place of the Torsen mechanical Q2 differential, there seems to be a fundamental misunderstanding of its function.
In a 2007 car, when accelerating out of a corner it is conceivable that the torque would result in the unloaded inside wheel, spinning up with excess power. Under this circumstance, the ASR/traction control system would cut in, reducing engine power to the point where the spinning stops.
In the 2008 chassis, the sensing system instead responds by applying a braking force to the spinning inside wheel. The engine continues to produce the same torque - ie there is no engine management taking place. Instead, as anyone who has ever played with a differential setup on an RC car or a Meccano set would realise, when one wheel is restrained all the torque is transferred mechanically to the other (in this case the outside) wheel. In other words a proportion of the engine torque is transferred to the wheel with the most grip, thus replicating to a degree, the effect of a mechanical limited slip diff. As it is not intended to merely cut the engine power to regain traction, it should have a positive effect on cornering.
If it is done correctly, and the jury is still out on the Alfa system, there will be an increase in traction. A similar but undoubtedly more sophisticated system is fitted to road going Ferraris as the E-Diff, albeit a rear drive system.
There is an explanation of this on the Alfa site somewhere.
Seems a shame that they couldn't use the mechanical Q2, maybe they are saving it for the MY2009 models with the new engines? In the meantime electronics will have to do.