The 787 APU was the proverbial POS at Entry Into Service - despite getting serious attention during the design phase for ETOPS. A big part of that was the (incredibly stupid) decision to do a complete clean sheet APU design and installation -
without referring to decades of lessons learned with previous Boeing APUs.
A few years after EIS, I was involved in a design review of the APU Controller (aka "APUC"). Some of the design decisions were mind-bogglingly bad. As just one of numerous examples, a standard design practice on the engine FADEC installations is that the FADEC is powered by some sort of dedicated generator/alternator on the gearbox, with aircraft power as a backup if the ded gen failed. So you effectively had power supply redundancy (the engine driven generator being required for dispatch). On the 787 APUC, the also used both ded gen and aircraft power, except that instead of redundancy, the design required
both to work properly - so the loss of
either one would cause the APU to shutdown
Due to requirements of ETOPS, the 787 APU was one of many areas that received great attention to correct the many shortcomings that quickly became apparent after EIS.
Good to hear it apparently worked...