To be completely frank - Skype has saved me TONS of money. I used to have such horrible phone bills - mostly from calling my dearest friend in Texas - but since Skype made flaterate available world wide, I'm in good shape! I pay 12 USD per month and can call virtually limitlessly to most western countries and then some. I can also have forwarding to my home phone if I'm offline on Skype, which also falls under the flatrate.
Skype has superior sound quality, unless there's a glitch, but if there is a sound issue, usually you can fix that by hanging up and dialling back. It's easy to maintain your address book, and naturally it is free to call computer to computer. You can also choose to pay in advance and have a pay-per-minute rate (really cheap compared to some providers).
You can also do a four-way conference call, video conferences, and play games together if you're so inclined. There are tons of secondary programs, created by other people than Skype (but usually authorized by Skype) that can be really useful. Sharing documents etc, for instant.
If you haven't tried Skype yet - I strongly recommend you give it a chance. It doesn't matter if you use Windows XP, Vista, Mac, Linux, Ubuntu, Windows Pocket PC...they have versions for almost any operative system.
And just so you know - LOL - NO, I don't have stock in the company, nore do I get anything for plugging Skype. It's merely a question of wanting to pay the good stuff foward. *smile*
So - if you're interested - click below and go explore a good way of staying in touch with friends - whether your next door neighbor or your good friend on the other side of the planet.