I like my Galaxy S4 a lot. It is a snap to use, fast and smooth even with 8-pages of apps, dozens of photos and videos. (Absolutly 0-problems with speed and overall performance.)
My only small gripe is the battery life. It doesn`t seem to last all day long like my former Black-Berry. The Battery Doctor app on google-play is quite useful in shutting down apps that run in the backround, extending battery life. Apps and screen brightness seem to be the main reason for battery drainage in any
smart phone.
95% of us will be using these phones in some sort of light source (in or outdoors). Why not engineer a phone that could take advantage of these light sources with temparary solar-energy through the camera lens. In weaker light sources the camera could digitally amplify the light sources, putting the battery on "sail" or temporally shutting it off without notice (like stop-start for example). This could greatly extend battery life throughout the day and you could brighten your screen to it`s highest setting in direct sunlight or other light sources without it affecting the battery. Just my 2-cents...