Had landline with them since 2013 and my connection since 2010 though left for a year as they were at the time subject to BT's awful Dynamic Line Managment which clobbered my long line on ADSL but unfortunately there was little they could do so switched over to an LLU provider.
Came back when they rolled out LLU in 2014 and haven't looked back (went FTTP with them in Jan '18)
99.99% of the time the service just works and when it doesn't they get things done quickly to get it working again.
They are also a real pleasure to deal with if you need to.
Virgin (ADSL) => Namesco => Newnet => O2 => Plusnet => Zen => Newnet => Zen => Freeola => Vivaciti (using O2 Wholesale DSL) => Xilo (C&W Wholesale) => Xilo (O2 Wholesale) => Xilo (TT Wholesale due to O2 Wholesale closure) => Zen LLU => Zen FTTP (39.5 Mbps down, 9.5 Mbps up)
Router: Fritzbox 3490
Note: I don't lay turf for anyone. astro or otherwise, all views and opinions expressed are my own based on experience.