Really. At least in my play group, we took Con very seriously, as everyone wanted as many hit points as possible. Also note that the limit of being raised is your Con score, and everyone wanted the highest system shock possible, as our DM's were ruthless about making us check for it.
"System Shock survival states the percentage chance the character has of surviving the following forms of magical attacks (or simple application of the magic): aging, petrification (including flesh to stone spell), polymorph any object, polymorph other"
And yeah, I noted back that magical aging causes System Shock as well, so I can tell you, I myself avoided spells that age my character like the plague, lol.
Turns out casting Slow on a bunch of enemies was about as good; I never so much looked at Haste twice until 3e. Do note that modern Haste already has a big downside, and the upside is nothing like "double your attacks per round"!
And no, no Dragon PC's. But in one AD&D campaign I was in, just about every spellcasting Dragon I fought had the spell, which was not only nasty on the face of it, it was the DM's explanation for why there were so many powerful Dragons running around (because of course, as monsters, they didn't have a Constitution score, so what system shock?*)
*The DM's words, not mine. I thought that was hogwash at the time, but I couldn't find any official rules saying otherwise at the time (but the answer is in Dragon # 133 if you're curious).