The primary difference between the two models is the 2pt touchscreen, the digitizer chip used for the touch control, and a different audio chip (we'd need to double-check our sources on that one).
Otherwise, all is the same in terms of user interface and whatever a how-to guide would tell you.
hi keith, is the user manuel for the a816 the same as for the a820. if so can you please email me a copy of the a816. i know there different just a little, but i think that manuel would work. would really appreciate it fi you could email me that manuel can't find it any where. thanks