Solid research on this exists, so there is not much to deny, at least when your goal is selling to the average user.
But: where is this magical place where people put heavy emphasis on performance? It certainly isn't here, and I would like to visit it for once. Companies caring, or giving their programmer the time to care, about performance are absolutely a rare sight. Unless they work in areas in which they are forced to care about it, and even then many stick to the minimum.
Snappy, low latency software is such a delight to encounter because it is just so damn rare. Especially on the web, I constantly feel like I'm wading through molasses, and the only reason I am able to endure this constant, agonizing pain is that I've gotten so used to it...