The two we have in our church are early ones (Summer 2001) and had all the early problems: flue hoses failing, poor ignition requiring PCB replacements, brittle condensate traps breaking and igniters needing to be replaced. To Keston's credit they fixed the early problems under warranty and picked up the later ones when we took advantage of their summer service offer (£75 or so per boiler including any parts - they fitted the improved ones without being asked to) and last winter, for the first time, both boilers ran without a missed beat - no ignition fail lockouts or anything else - so when Keston didn't offer us the summer service this year I decided to leave well alone.
The one I fitted at my mum's house three years back has been fine, save for one failure that I embarrassingly failed to diagnose: a blockage in the hose leading to the condensate trap.
Parts availability, when I've needed it, has been disastrous. In virtually every case standard service parts have had to be ordered from Parts Center and in one case when a condensate trap still hadn't turned up after three weeks I wrote to Keston's MD who sent me one gratis - Ok but had I been a professional installer I would have been seriously upset at my wasted time and having a dissatisfied client. Hopefully now they're part of Ideal, things are more organised.
Having two in the church at least gives a fallback. In a domestic situation, having one and not being able to get parts is a major issue. My Glow-worm Cxi at home is now all but four years old and hasn't missed a beat. Couldn't get a replacement igniter gasket off the shelf at Parts Center though and bizarrely this and the burner gasket are not on the short parts list, although non-service parts are.