I'm one of those unlucky people who has no luck with boilers. I've lived in 3 houses in 12 years and gone through 6 new combi boilers. I can't remember what all of them were called but the ones I had the most trouble with were all Baxi. Touch wood, my latest one has given me no trouble since I had it installed 3 years ago...it's a Worcester.
We have had a Worcester for just over a year. We did have problems with hot water but Worcester came and fixed it. The heating no problems. Unless things change I would have another one if I moved. Rgds Al
One that has been correctly installed, correctly commisioned, and serviced annually. Regardless of make !!! They are only as good as the person who fit it. Having said that I would avoid the cheap nasty ones you get from DIY outlets. They are not very well thought of in the trade. and not very reliable
Vaillant are fantastic boilers, they are extremely reliable, BUT can be a pain if they do go wrong as most CORGI reg engineers find them a bit of a pain to fix as they are very complex - having said that though, I have very rarely come across a Vaillant that has gone wrong, they are robust, sturdy boilers.