I recently moved and tried using my cell phone exclusively. Didn’t work. I decided that I needed a house phone. However, I use a house phone so infrequently that it really isn’t worth $20 per month to the cable company. I decided that I could try Skype. I found this usb phone on Amazon for $6.40. A Skype subscription is $2.99/month plus $3.00 a month for a DID (phone number). That puts me at $6.00 per month using Skype vs. $20.00 using cable, which is a savings of $168.00 per year. (Probably more when you consider that Skype is not a common carrier and so they don’t charge FCC taxes, universal service fees, or 911 service fees)
So far it has worked great. The caveat is that it only works for Windows. However, I leave my Windows 7 VM constantly powered on in VMware Fusion so I connected the USB device to that VM. Once I installed the driver I noticed no audio quality issues. It sounds much better than my cell phone!