Yes I use Skype all the time for messaging and telephone, we also use it at work and the telephone charges are tiny compared to other providers call costs.
Plus its handy to call people whilst you are sitting at PC doing other stuff (like looking stuff up on AB !!)
I'm going to be using it more when I play World of Warcraft, helluva lot easier to say/ tell what you're going to be doing next rather than typing it out.
Skype is telephone over the internet, with instant messaging too.
I do not have a landline at all and use Skype for all my calls - I have a Skype telephone number so people can call me at their usual rates.
I have a wifi telephone - the 'sender' plugs into my router and the telephone works from that. My pc doesn't need to be turned on to take and make calls.
It saves me a lot of money.
I also use the Instant Messaging a lot - it is excellent.