IDNet use Zen’s network, historically that wasn’t a bad thing, but it does mean instead of your ISP having direct access and control/monitoring of it’s network, you have added a layer of complexity whereby any issue now needs to be investigated initially by IDNet, then logged with Zen, and you wait for Zen to come back to IDNet who then come back to you. In fairness, it’s not that much different to any of the other small providers who subcontract backhaul and/or core functions to a 3rd party and don’t own/operate themselves, and it’s unlikely most people will ever experience (and notice) something that requires this level of investigation, other than perhaps via a large scale issue, and that’s going to get a priority response anyway.
As to quality ISP’s, Martin @ Aquiss is top tier, professional and knowledgable, he’s also happy to help and advise, the only issue is you are buying ‘Martin’ and while he is amazingly responsive (even out of hours), a point will come where that doesn’t scale. Other considerations are he’s PPPoE only, so for devices like the UDMP/SE etc. without hardware acceleration, that’s potentially going to be a problem, but firmware updates seem to have made it less so at gigabit speeds.