When a company develops and/or releases new hardware, then later release an update. Those little creases discovered in the original revision should be resolved, right? Therefore offering an improvement. In the case of Apple and their mobile computing equipment this isn't so, often they introduce new hardware with new features which usually avoid the the issues of the last generation and also introduce a whole new problem.
For example, ever since Apple introduced their MacBook series, the built-in audio hardware still producing imperfect sound, still suffering from electrical isolation issues hence 'buzzing' with the occasional 'pop'.
In the case of Battery technology, I think Apple shouldn't be wasting time and money doing the research themselves, instead they should deploy a dedicated department into new researching what could be utilises to better/improve their range of products.
Agreed. this adds to the cost to their products.