Skype for me has always been fantastic. Never failed to let me down once, unlike MSN which frequently has problems. Calls are clear and you can literally talk for hours without any problems. I find MSN is more for kids and with Ebay buying it out and slaping it all over its site, traffic is growing. Bottom line is that if everyone in the future has a pc or plasma/pc media home setup then BT and Ntl will be a waste of time. Plus you can use the camera to see them on screen. A bit like when the Naked girl randomly rings up Stallone in Demolition man, but not as advanced/ full screen (yet).
Obviously if you get Skype credit so you can call landlines and mobiles it will be fine as well as cheaper but if that person uses the Mic/Speaker combo you might find it slightly annoying if they do not have the volume levels for the room adjusted correctly. A proper dedicated headset is far better so that it seperates the ear section so you can not get that down the line too.
You can get various types of skype phones now and not just those from Skype.com shop, which allow you to view contact lists on phone from the sofa or whatever and call but units like the one below which permit you to use your standard home phone or mobile.
http://www.boysstuff.co.uk/product.a...id=&src=Search
http://www.firebox.com/index.html?di....y=0&Submit=Go