Here's my reasoning against skype.
I have two microphones. One is an inbuilt microphone and I cannot turn it the forget off except by plugging in the other. This microphone is beneath my spacebar, and as such when I am typing everyone gets spammed with loud clicking noises, and on top of that, the quality is ass and I have to talk loudly to get it to pick up my voice.
The other microphone is external, a set of Logitech headphones. They are uncomfortable as forget to actually wear, and despite configuring them to pick up in area mode, they actually don't. I have to wear the headphones to use the microphone at all, and still have to talk loudly.
Because I'm usually up in the middle of the night, I can't really talk loudly, since my bedroom is only one wall away from another one on either side. Hence, I would not be using Skype's voicechat.
So why the forget should I use Skype, if I'm just going to do the exact same thing with it as I do with MSN?