I have not used their Home Phone Service. But, I have in past used their "1010 DialAround" long distance service with good results.
My brother in New Mexico is using Yak Dial-Around service to call Brazil and is happy with it, too.
But as a home phone replacement service, I can't really say.
I will presume their backbone carrier network is the same for home phone as it is for dial-around service - VoIP based.
For any given company you will find both people who love the service and people who hate the service. It boils down to their "personal experience" with that company. And, unfortunately, customer service experiences vary widely from one person to another - even with the same company. I guess it comes down to "crunching the numbers" - those who love it vs. those who hate it, or vise-versa. And, typically, those who hate something will be more vocal than those who aren't having any problems.
Yak Canada has been around for a number of years and are not fly-by night. However, I understand that Yak USA is a newer venture and there could be some problems on that end getting things going. If there are problems, it could just be growing pains until they get their act together - in which case, you may want to wait by the sidelines and see what others are saying over the longer term....