I've posted a few times.. the reason we don't do a fancy schmancy 'overlay' screen when you push a button, like PSP/PS3, is because it needs lots of work and we donm't have the blood to do it -- if anyone has spare timke and knows how to code, feel free
(remember, all of this is done in spare time.)
ie: a PSP and PS3 is solely controlled by Sony, with a single way to render to the display; here, we're a general purpose machine (not just a single controlled game machine), so applications can render to framebuffer, or use GL/GLES, or use X11, or SDL, or any number of ways of getting at the screen. Doing a 'good solid' job of doing an overlay over all of that, that also handles lid open/close and properly manages input (ie: so overlay is up, input goes to overaly not to the apps underneath)... its actually quite a bit of work.
(Think about coying a file.. users think about how easy ti is -- just copy and paste a file; but in pract,ce develoeprs have to wrry about if theres space free, if the source or target is over a network and what protocols, data integrity and compression, any thousand of things. Same for overlay.. it may sound easy, but theres more to it than you think
jeff