Well as my car is rather unwell, I've been loaned an A3 Saloon. It's similar to mine in that it's the 150PS diesel, S-Line in Daytona grey so I thought it might be useful to share my observations comparing the two.
I like the shape of the saloon - a lot! I've always had 3-doors, sometimes (my first 8P and the current 8V) because that's all that was available when I had to order, but also because I don't often have people in the back and quite like the larger front doors and having the B-pillar further back. That said, when I do have people in the back, it is a pain getting in and out and it's a bit of a squeeze for legroom. Whilst the old 8P had the same wheelbase on all models, with the 8V, the Sportback and Saloon actually have a longer wheelbase so, in addition to the extra doors, there is noticably more legroom in the back.
The shape itself is very nice. It looks like a slightly smaller but sharper A4 and just a bit more "grown up" than the hatchbacks. I've always been concerned about a loss of practicality with a saloon but I have to say the boot is cavernous! Ok you can't remove the parcel shelf so high items might be a problem but, in terms of actual volume, there's more space in there than in mine, by some margin.
The saloon rides slightly better and slightly quieter than mine. This is no surprise as the longer wheelbase will always result in a better ride and the three-box design of a saloon tends to isolate noise from the back better. Interestingly, despite having the same wheels as mine, the saloon is on Conti Sport Contact 2 tyres, as opposed to the SC5s on mine. What the exact difference is I don't know, nor whether it's contributing to the better ride.
I'll share some observations on equipment and options too, although I appreciate these aren't specific to the saloon...
This car lacks both the Tech Pack and B&O sound I have in mine. Obviously the most noticeable difference with the former is the smaller, lower resolution screen. This is a huge difference to me, but possibly only because I'm used to mine. I'm sure it's fine in isolation but, compared to the Tech Pack screen, it's a big step down in my view. As for the sound, the car has the standard sound system which I have to say is very average. It's ok at low volumes but jack it up even a bit and it doesn't fare very well to be honest. Again maybe I'm just spoilt by the B&O (and having had BOSE in all my previous 8Ps) but I'd strongly recommend speccing at least the Audi Sound System if you like listening to music on the move.
The seats are the standard S-Line ones, whereas I have the perforated alcantara/leather ones. They feel just as comfortable to sit on but they're noticeably more slippy than mine and don't look or feel anywhere near as nice, but then you wouldn't expect them to really.
It also lacks the interior lighting pack, so no LED overhead lighting or strip lighting details. This does make the car feel a little less "special" when driving at night but that may well not matter to many. One thing I did notice when I first got mine is that the use of LEDs for the overhead lighting produces a very "cold" or "harsh" light which I don't care for that much. I actually prefer the regular interior overhead lighting as it produces a softer light.
As for things this car has which I don't, these include the park assist and hill hold. The former is a nice-to-have I guess but hardly essential. It's kind of cool seeing the graphic on the MMI display when it's in operation but that's about it - the standard rear parking sensors I have are more than adequate and there are many other things I'd spend money on before I specced this.
The hill hold is a different story and I'm quite impressed by this. I actually think it's mis-named and should be called "Auto Handbrake" or something. The standard car will hold the brakes for a second or two when you release the footbrake whilst on an incline, to stop the car rolling back and I was under the impression that the hill hold just extended this function to work indefinitely. In reality it seems to do far more than that and basically holds the handbrake on every time you stop, no matter what. I'm actually finding this quite useful as, once you've come to a stop, you can safely take your foot off the brake all the time, then just drive away when needed. I think I'll spec this next time.
Hope this ramble is of use to someone