Back at the day I used to recommend dual core processors to my friends precisely becase of one reason:
Since there are not that many applications at the moment utilizing the power of two cores, the best use case for them is this: when your application hangs up it sometimes eats up to 100% of your CPU and you you cannot even move your mouse or click anywhere simply because there is not enough processing power left. Now with two cores, when your application hangs up like that, you still have that second core sitting idle in the background and you can quickly bring up task manager and kill the misbehaving app.
Nowadays, when by far the most used and abused application is the web browser, and when each tab is its own process, from time to time I see all of my cores – two, to be exact – being fully utilized up to a point that typing or switching to another application becomes almost impossible. Even mouse movement becomes shattered (and I’m on a Core 2 Duo 2.53GHz). I feel like being back at the single core times. Four cores might behave a little better, but maybe eight is the target to reach? I’m worried that the browser will just eat them up, no matter how many you’ll have.
Applications utilizing multiple cores are actually very appreciated, it’s just too bad, that this model has some drawbacks.