When it became clear this wasn't one of those one-and-done activities but rather a new routine, I decided it was time to find some prescription goggles. I was hoping for ones that would let me have a different prescription in each eye, since the astigmatism is fairly different between my eyes and when you buy something like goggles, the adjustment is to the diopter to compensate. Swimoutlet.com's goggles do not appear to be available with a different prescription for each eye. However, http://www.aquagoggles.com/ offers them. They ship from Canada, so you'll not only see the approximately $30 charge for the goggles plus shipping but likely also a charge for converting currency (nominal for me -- YMMV).
I've only used them once; I'll update if things change. They fit well. The case is nice -- my glasses fit nicely in it when I have the goggles on. I can see fantastically well with the goggles on. They didn't fog or leak. They remained comfortable for the half hour I had them on.
It's hard to convey just how exciting this is: I'm used to really unpleasant vision/swim experience compromises in the water. I have no idea why I didn't do this years ago; I was operating under the assumption this would be a lot more expensive and difficult than it turned out to be. If you swim, and you are really nearsighted, you ought to get a pair (they do farsighted, too).