I have a non-P Sig as well.
The Sig options were Performance, Pano roof, and rear-facing seats. I believe the prices were $10k (pretty sure on that), $1500 (positive on that; it's on my sticker) and $1500 (least sure on this one).
We got the pano roof, but no Performance or the rear-facing seats.
I too remember that some non-sigs were delivered before all sigs were; but I can't remember if only sigs shipped in 2012. We got ours in Sept 2012.
As for ride quality: the Model S is definitely not the plushest car I have been in. But for the level of performance it offers, I think it's pretty good. I am perfectly happy with it. This is hard though, because not only do people have different backgrounds and expectations, but the cars can vary with age, suspension, wheels, tires, etc.