Even though I'm weird and read manuals, I can't remember everything :)
So, the audible battery warnings of 'battery weak'(<30%) and 'battery very weak'(<15%) would be more useful if they actually stated the percentages, i.e. 'Battery 30% remaining', 'Battery 15% remaining' etc.
Or even better would be an estimation of battery time remaining, e.g. 'Battery 1 hour remaining' etc. I know this is techically more difficult, but I have several bits of softeware on my PDA that puts a time remaining figure on battery life.