The facelift is more than just a few updates. I've had the 'opportunity' to directly compare 5000 miles in a very late (April '16 build) PFL S3 with my new facelift S3, and while I've only done a couple of hundred miles in the new car, already I've noted a number of things that have been improved, even if only in the most minor way. These tiny improvements add up to a car that 'feels' rather different to the one I just handed over.
Even tiny things, like the way the parking sensors gently fade to silence when you've stopped approaching an obstacle are a godsend. I had a new Astra a few weeks ago, and the parking sensors were loud enough and insistent enough to actually spur me into looking up a Spanish translation for 'parking sensor' so I could pull the ****** fuse.
The cabin is quieter (this may or may not be a function of not having pano roof anymore), the MMI talks to Spotify on my phone. The MMI dial turns the correct way to go up and down menus. I can advance and rewind tracks on the steering wheel (a major irritation on the PFL) The headlights are little short of amazing, and make the PFL LED's look like the hopeless rubbish they are. The B&O sounds better than the old car.
The car doesn't feel any faster, despite its extra power, but it does feel 'better'. There's something I can't quite resolve in the behaviour of the chassis that makes it markedly nicer to drive than the outgoing car. Certainly the steering feels more talkative (could be the different tyres though), but there is a quality in the ride that wasn't there before though. Sadly my **** is not finely tuned enough to tell you what exactly it is that's different, but it definitely feels 'better'.
Of course, none of this is really sufficient reason to change from a PFL if you already have one. These are what I've discovered after a couple of hours, and I imagine there is yet more to discover once I start playing with mag-ride and Quattro settings and throwing it through a few favoured bends. But based on my experience so far, I'd say the FL is definitely worth having over an older car, and given the choice there would need to be significant financial reasons needed for me to opt for an older car instead.