I had a 2007 S3 for a year. Bought it with around 110k miles, sold it a year later with around 125k. Bought it with a few problems (duff turbo valve, duff ac compressor, duff wheel bearing), but once fixed it was fine. Nothing else broke, put it that way.
They have a cambelt connected to crankshaft which is the standard belt to replace, but there's also a chain which connects the 2 cams together. This needs to be checked otherwise it gets expensive if it works its way loose.
Like the 1.8 and 2.0 TFSIs, it's not uncommon to end up with an engine that loves to drink oil. Mine didn't have any issues, but you read of some engines that require more than one litre per 1000 miles.
The car itself is standard Audi fare, so a well-built interior goes well and grips like there's no tomorrow, even in the wet. As expected though, the suspension is very hard and it's not particularly involving to drive. It's great at what it does though, which is going fast with minimal fuss in all weather conditions. Just don't expect it to be a particularly engaging or dynamic drive.