pageoneresults - 3:11 pm on May 19, 2011 (gmt 0)
It's what is acceptable to the visitor, what serves them best.
That's the bottom line too. There's also the "perceptual" load time to keep in mind. You can have a page that takes 4 seconds to load but for the visitor, they may never see that latency. It all comes down to how you serve the content, and what order it is served in. I'm referring to the very start of the process from the moment that page is requested by the browser. As long as you can fill that viewport with relevant information, that's a +1.