Use Cases and Deployment Scope
I have multiple clients using Lumen/CenturyLink for SIP handoff. The experience is mostly positive, but there have been interruptions/downtime. I believe there are better providers/solutions out there if you are willing to spend a bit more.
The benefits of SIP are resiliency and failover that traditional PRI and traditional voice trunks don't offer. The disadvantages are that the voice quality is dependent on the ISP/carrier for quality. In this case, Lumen/CenturyLink.
Other Software Used
Comcast Business VOIP (VoiceEdge), Broadvoice, Nextiva Business Phone Service, CenturyLink Fiber + Internet, CenturyLink Hosted VoIP