What, exactly, are you basing this vitriolic assessment on? You're not an installer: you described yourself as an amateur ("My amateur opinion" - Tuesday 1st December)
Take a look at your list - it sounds like the sort of thing a mischevious schoolboy writes on the blackboard when the teacher's out of the room. What's the justification for such language?
You said in one of your posts, that you were considering replacing your present boiler with an Intergas - later on in the post you your actual words were :- "By the way, Intergas also do a budget boiler which I've heard great things about" ......
.......... but now you can't find enough abuse to throw at them.
What first hand experience do you have of Viessman that has brought about that crass collection of invective?
Of Baxi you said .... One of the best things about Baxi is that they react to feedback and have improved the latest model. The latest model is £550 and has a stainless steel heat ex and all brass diverter + they've increased the warranty.. so you wouldn't even get the problems I had. A steal at £550. By the way this boiler is the same under the hood as the Baxi 800 (which costs 1K+) ...........
.............but you now call them a 'boxofshite'.
I won't repeat your judgement upon Vokera.