Scoble links to a piece at Scobleizer: Microsoft Geek Blogger but has the more salient quote himself:
At Winnov we used to ask “what’s the OOBE like?” The “Out of Box Experience.” The first hour of a product’s life will determine whether or not you’re fantastically in love with it or not.
And: My coworker, Jeff Sandquist, even quantified it further. He only gives a piece of software a week. If he is still using it after seven days, he’ll keep it, but if it frustrates the heck out of him he uninstalls. Getting adoption requires paying a huge amount of attention to the first few hours of experience.