I would never, EVER change VOIP services, ever. Skype is the best decision we ever made for our phone services provider. It's cheap and reliable, and saves us a ton of money every month!
For three dollars a month you can get free nationwide calling within the United States AND Canada. Plus, for a small extra fee, you can set up your own special phone number. Without it, you can still have them call in via Skype, or you can call them. However, having our own special phone number was just so convenient, plus you get to pick your own last four digits.
It's also one of the most reliable VOIP services I've tried out. With the one exception of the Great Skype Blackout a few months back, there has never been a single burp in our connectability. The phone quality is also great, and on occasion you will be asked to submit a one click form asking about the quality of the call. Using that data though, they are better able to tweak your calls for better quality!
Skype is seriously the best service I've ever used, and you can't beat it's price either.