The flip-side of this is that if something is too fast, it raises doubts about whether it actually happened at all. I'm reminded of the TurboTax case, where Intuit found that adding a bunch of artificial loading screens to make it look like TurboTax was taking its time to really pore over customers' tax returns ended up being more appealing to users than not doing so. The actual "analyses" happen within less than a second, but that was (allegedly) too fast for users to believe.