My wife had considered getting rid of her home phone service and go with just cellular, but prefers the ergonomics of a portable handset for long phone calls. When I recently was switching her mobile service from Telus to Roger/Fido, the fido agent offered their wireless home phone service for $10/mth. He also offered $50 in credits after two months to offset the $30 one-time cost of the adapter. We decided to go for it.
Before the phone line adapter arrived, we received a shipping confirmation from fido which indicated the adapter is a ZTE WF720 which AT&T wireless has been using for their service in the US for the past year.
The adapter arrived by UPS, and included a fido 3G LTE sim. I tried the sim in my unlocked phone, but it is pin locked (until I figure out how to crack it!). So I installed it in the phone adapter (in the battery slot compartment), plugged in the battery & power, plugged in a phone, and got dialtone. The sim was pre-programed with a temporary number to use while we wait to port the land line.
The sound quality is typical of a gsm codec - adequate but not as good as a land line. For the heck of it I tried sending a fax, and it negotiated with the receiving side but failed on page 1. So it's fine for voice, but not for data. For the price, I can't complain.