At a price, though: high-index plastic has much higher dispersion than the lower-index materials. This causes a greater "prism effect" near the edges of the lens, which interacts very badly with the new RGB-backlight monitors [0].
I had a bit of that when I got my next-most-recent pair of glasses. It took less than a week before I stopped noticing it entirely.
I don't think my current pair have the problem, but I'm not sure I could tell any more.