i wouldnt say that OS guys cut corners, considering that nearly everyone outsources phone OS dev to symbian, linux/windriver/montavista, wince
i think its more a case that you make do with the hardware you are given and i think that holds true with the epoc example you mentioned
the new arm chips are great and feature rich, they have had a mmu for a long time but it can be an advantage somtimes to turn that stuff off, shock gasp horror i know but i have heard of people turning off the mmu and cache in arm chips so that the timings are predictable which for dsp work with a base band processor is critical
i think we are really forgetting that embbeded development is really a diffrent world and is driven by diffrent market forces, in the mobile phone world those market forces are the telcos, they can say what is and isnt allowed on thier networks and cingular and the others relise this. i also belive that they relise the customers would be willing to rip thier throghts out over somthing they cant fix due to the botched and weakened implemintations (thank you nsa)
in relation to the iphone, its market angel is somthing i simply cannot fathom, i see it but i dont understand it, but i say the same about windows. its alien to me and some of thier postions are plain wierd however i belive for them to come out on top they have made very correct decissions at the cost of the user, though they will never know it and its not that bad because the top can be lonly and complicated (try explaining how thi internet works to someone)