The connection it provided was stable and consistent as an internet connection, and they were very good about the SLA and were on top of outages. They were honestly the best ISP I've ever dealt with. But, we never used it for voice. I imagine they would not have been able to get away with that set up if we had wanted to use it for voice as well.
I felt a little ripped off when I saw how they were presenting us the T1 connection. I would have rather purchased internet access via bonded DSL lines than the pseudo T1 that we got, but it was not available to us at the time. I blame the local telco. I asked the phone company technician about it and he told me that they had basically stopped running T1 local loops whenever they could.