The world's fastest typist, Sean Wrona, would abhor that - he uses capslock instead of shift(!) He can go 200WPM+ so, clearly he's doing something right...

I assume there's a point in overall speed where the slowdown from caps-up/down -> letter-up/down -> caps-up/down is worth the reliability drop from coordinating shift-down -> letter-up/down -> shift-up. I think I hit that point sometimes entering passwords and other frequently entered info, but the reality is for most typing none of us get there.