I've used Voip.ms as my primary phone service for years and it's been very reliable. Voip.ms is one of only two VoIP services that has a Gold Award at DSLReports:
I also have a Google Voice account, but the service is less reliable than Voip.ms, and I only use it to call a couple of family members who use Google Voice as their primary phone service.
I ported my old Voice number to voip.ms too.