Help Or Hindrance.
I'm not one of the people predicting the demise of Microsoft anytime soon, but the amount of discussion that has surrounded the elimination of the hated Clippy from the latest incarnation seems to me to to be symptomatic of what irritates their detractors. The perception that they (like so many other companies) believe they know what's best for the user.
Where they saw a proactive user-friendly pop-up, many users saw an annoying imposition and one that was exacerbated by the fact that, until XP came along, it was up to the user to switch it off. Every time you make a wrong guess about your user, you're in trouble and you're sapping enthusiasm. Sadly, this is repeated in the advertising for the Vista launch.
In addition to being an irritating phrase that's imposed on my life far too often by home improvement and makeover shows, the "wow factor" is subjective to the user, so declaring that your product will wow me can only lead to irritation and/or disappointment.
Real proactive attention to the user experience should never result in unwanted interruption. The key is to make it easy for your user to access solutions when and how they want. This does not mean imposed FAQs, but it does mean intuitive, searchable help options; it does not mean expensive, automated and unresponsive help desks, but it does mean easily accessible human reactions (as the user-created sites www.gethuman.com and www.saynoto0870.com show); and it most certainly doesn't mean you telling them what it is they want. That's for them to tell you.