Covad is using Cisco. The big benefit is that Cisco offers very rapid replacement, usually within 24 hours when their systems go down.
The second big advantage for using Cisco is the ability to have a standard managed network across all of the Covad facilities and to find Cisco qualified engineers.
When you look at Cisco you have to admire how they market IP the way Starbucks markets coffee. The ability to build an organization that is so homogeneous and has been able toscale is very impressive. While their tech is often bought in to the fold, they do one of the best jobs of integrating emerging technology into their network hardware architecture.
By choosing Cisco, Covad has pretty much cast their lot with them as they did with data in the past. I don't think anyone should be too surprised.