Their boilers are made by simple designs and they have a reliable performance reputation.
Worcester use aluminium for all of their main heat exchanges. Compared with stainless steel heat exchanges used on Vaillant, Viessmann, and Baxi, aluminium has a good heat transfer rate, but bit less quality on life span. If from the same boiler manufacturer like Vaillant, the boilers with stainless heat exchanges will be expensive than ones with aluminium heat exchanges.
WB also use more plastic parts instead of brass parts.
Worcester Bosch are good on marketing, they are targeting on the installers with average competency levels. WB are not on high end market which only counts for 5% or so. They are not the industry leader on modulation system controls too.
In last 20 years, WB have had a terrible design on the hydraulic side of all their boilers, it will be a terrible job for any gas engineer to change a simple PRV.
Overall, WB offer reliable and bit over priced boilers.