Can anyone confirm whether the quattro system on the S3 is the same as the A3 and the TT.

According to Audi.com the quattro system on the S4 and S3 is different and the S3 is not permanent four-wheel-drive.

See Quote Below

"The Audi TT quattro and the Audi A3 quattro have been equipped with the latest quattro technology: the electronic-hydraulic multiple-disc Haldex clutch. It reacts quickly and sensitively to all kinds of driving conditions, and - under the influence of multiple parameters - effects a dynamic engine torque distribution between front and rear axles. The system is also active in reverse gear and turns off automatically if ABS breaking is implemented - the ABS can operate in optimal mode."

Jason

Yes it is the same. All transverse engines (A3 S3 TT Golf) have the Haldex system whilst A4 A6 A8 have torsen supplying equal drive to all wheels , until one starts to slip.
Check out the previous posts in this forum for comments on the effectiveness .