I have an '05 9-3. It's not the Aero, but the 1.9 TiD 150 Vector.
Obviously it's not as quick off the mark as the Aero, but for overtaking performance it's pretty similar (due to huge torque of the diesel engine).
Handling is not too bad, bit wallowy as others have said and has a strong tendency to understeer - personally I wouldn't want to put a whole load more power under the bonnet without sorting the handling first.
Ride is firm but not as firm as the Audi A4 and there's quite a bit of road noise transmitted to the cabin, which I guess would only get worse with stiffer springs.
It's not quite as low as the Aeros (I think), but I still scrape the bottom of the front bumper quite a bit when coming down over speed humps (going up is usually no problem though).
Build quality is OK, few squeaks and rattles after nearly 2 years and it's been in the garage about 4 times to have a seriously squeaky steering column put right (actually going back again for the same thing soon).
Looks wise I think that it's one of the best looking saloons out there, particularly from the side profile, but that's just my opinion.
Hav
/edit A few of other points.
In the saloon, while the boot is a good size and you get split/fold rear seats, the boot opening is not huge so getting big items in can be a PITA.
The standard 'half-leather' is a bit of a fib. It's more like 1/4 leather (seats are leather faced only), 1/2 fake leather & 1/4 material

That said, the seats are very comfortable, but leg room in the back can be a tad limited.
The safety rating of the car is 5 stars for occupants (it's crammed with air bags and other safety features) so a good choice for a family car. Unfortunately it's only rated at 1 star for hitting pedestrians - ho hum.