We utilize Windstream for managed MPLS and managed firewall at our remote site (4 locations). Their firewall team never communicates with their network team to the point where they often 'forget' that they own the firewall at each site. I often have to convince/remind them to talk to the other group when troubleshooting issues.
Implementation was awful. They regularly would be missing core people for implementation calls, forgetting either a voice engineer, network engineer, or firewall engineer, who were all required for a successful turn-up. In several cases, the implementation timelines were delayed by weeks or even months because they had not properly pre-qualified sites with the local loop carrier and needed to solve issues that they only discovered days prior to our scheduled turn up.
They have promised increased support, but upon adding our most recent site, the turn up was still poor, and we needed to troubleshoot issues ourselves due to a lack of support from the Windstream team.
Finally, reliability is average. We have seen an average number of small (1-2 hour) outages and a couple of high profile longer outages. I would say these average a small outage every other month and a large outage once or twice a year.
We utilize them for our remote sites to enable Voice, MPLS network connectivity and managed firewall. They accomplish this task, but only with a large amount of difficulty.