Over here in the US, I bought an Obihai 100 well over a year ago. I paid $44.00, connected it to my Google Voice account, and have had a free landline since. The downside is that my landline is not connected to the local emergency service. I still need to use a cell phone for that.
I have only once, for a couple days, had service problems that ended up being related to the wireless router it was connected to. Otherwise, the call quality is excellent.