Re: I've had no problem with BT
When I moved to BT in 2010, they were the only option other than (*hack* *spit*) Virgin for a fast service. I could bemoan the price of Infinity 2, but I've had the full 76Mbps from day one, Inf2 is unthrottled, and outages have been quite rare. I've zero doubts that Zen would provide better customer service, but I haven't needed customer service and so I stay where I am.
I think it would be a bit different were I to switch today. The VDSL2 modem is now built into the HomeHub, which would make running my own OpenWRT router slightly more complex. I'm sure it's still doable, but just more annoying to actually have to deal with the HH instead of having it in a box in a locked filing cabinet in the basement where it belongs.