One thing I've noticed is how I find myself more impressed with the sport than the Olympics, but exactly not for the obvious reason. It's just more obvious how much effort is going into it, compared with the 'regular' Olympians, who sometimes just look like automata. I noticed it in the dressage especially - I know lots of you don't regard it as a sport, but bear with me...
I've ridden a bit, badly, and I know how a rider ought to look on a horse. Toes forward, lower legs gripping well, straight back, hands close together and low down on the horse's neck, bum glued to the saddle. I see the Olympians riding and think "Well, of course they are good, they've got it all right". Watching some of the Paralympians, no stirrups, toes turned out, seemingly bouncing about in the saddle, hands all over the place, and I think "That's what I looked like most of the time!". And yet they are achieving perfect results, whereas I was generally mostly at the whim of my mount whether it did what it was supposed to.
Similarly with some of the sprinters - limbs flailing about like a toddler running downhill, and yet I know they'd thrash me in a race, whereas Bolt just looked like a machine made to run fast, and I couldn't relate to him.
Interestingly, the one sport in which I haven't seen this effect is the cycling. Once on a bike, the Paralympians look just the same as the Olympians, albeit perhaps with one metal and carbon fibre leg or arm. Their disability may be obvious off the bike, but on it, it may not be.
So basically, I think I'm more impressed by the Paralympians, because they sometimes look more normal than the Olympians. (without in any way belittling their achievements)
Swimming, I'm just constantly astonished by. A man just raced breaststroke with no arms. My mind boggles at the thought.