Everyone's experience will vary, but for me, I've come to the conclusion that sapphire isn't worth it (beyond the ego boost).
I had the SS first-gen (S0). After about 2.5 years the display separated because the battery expanded (Apple replaced at no charge). I used the replacement for another year before upgrading to an S4 aluminum.
The polished steel on the replacement S0 (which I used for a bit more than a year) shows many small scratches and scuffs. My recollection is the original S0 had some pretty deep scratches in the case. I can't see any scratches/scuffs on the matte aluminum S4.
The display on the replacement S0 has one or two light scratches, otherwise looks pristine. My recollection of the original S0 was that it picked up some scuffs and light scratches - some seemed to the materials the watch contacted, like wall paint - sometimes I was able to rub those off, but it didn't all come off - maybe it was in the coating.
The display on my S4 has some light scratching/scuffing/marks that are only visible from certain oblique angles - I suspect they're in the coating, rather than the glass. It doesn't have any noticeable impact on usability - I have to be looking for them in order to see them. If I'm right about it being in the coating, then the same might have happened to a sapphire - the coating isn't any harder.
Altogether, considering the price differential and that this is a bit of tech that I'd upgrade after 2-3 years, I don't see the point of paying several hundred dollars more. I certainly would not consider the extra money spent on sapphire to be a substitute for AppleCare - a cracked screen isn't the only bad thing that can happen, and sapphire does break, it's just less likely to break.
Fact is, most of the wristwatches I'd owned earlier in life (Timexes, for the most part) showed much more damage - more and deeper scratches. My work was more physical in those days, but I think overall Ion-X Glass probably deserves a bit of credit too.