The main reasons for ST over S64 are 3D, smart apps, and wider choice of screen sizes. If those are important to you, buy the ST.
If those things don't matter, you are paying a *lot* of money for perceived PQ difference. I have never seen a comparison where someone has looked at the two TVs next to each other, both calibrated, and both the same screen size. I would hugely discount the opinions of folks who have already spent the extra dough for the ST.
The linked article says "We gave the ST60 and S60 the same 10 in value, but the ST's superior antireflective screen makes it much more versatile under all kinds of lighting. If you're not on a tight budget, it's worth stepping up to the ST even if you don't care about its added features like Smart TV and 3D." I would agree 100%, and since the S64 has the antireflective screen, that pretty much closes the deal IMHO.