Agree with HDTV101 - voip.ms has worked great for me.
The only reason I'm porting my number out is because I need a POTS line for an alarm system in a new house. Having my number on that line makes making and receiving local calls, and receiving long distance on the POTS line easy, and I don't have to pay extra for the routing through voip.ms. I still plan to route outgoing long distance through voip.ms because it's so cheap. Overall, I'll be paying more per month, so being able to save a few bucks on incoming or local, plus the monthly DID and e911 fees, without having to change my phone number is nice.