I have an A3 S-line, its a bit like the difference between an escort 1.6 and an escort Xr3i, it is basically the sporty model. Better exterior styling with larger alloys, s-line bumpers etc and then much better interior trim, nicer steering wheel, s-line seats.

Then on top of that you can pick them up with lots of additiona extra's.

Mine has:

Exterior:
S-line body styling with agressive styled front bumper
Auto Xenon headlights with follow me home function
Auto wipers
Headlamp washer jets
Audi vortex side skirts (rare sort after option)
Rear parking sensors
heated electric door mirrors
S-line sill kick plates
18" BBS slit rims


Interior:
Bose sound system
S-Line embossed half leather seats
Multi function S-Line steering wheel (stereo and phone controls)
In-dash 6 disc cd changer
Dual climate control
Auto dimming interior mirror
Underseat storage compartments
Fitted mats front and rear
passenger footwell and seat back cargo nets
Arm rest with storage compartment
Courtesy lights
dual vanity mirrors with lights
Drivers Information system
Aluminium inlays
Auto door lock
Parcel shelf sun screen
12v socket in boot
One touch electric windows etc

Depends what you want in a car, some of my mates are happy it goes from a to be and couldnt care less if it had nice bumpers, where as I prefer something that looks good and so am happy to pay extra or the extra's.