the old microsoft arc mouse due to the arc shape it naturally feels comfortable
has 2 buttons on top and a scroll wheel and a button on the left side operated by the thump , and its foldable to switch it off , so ideal as laptopmouse too ,
i use it all day long from morning to late night 7 days a week and still the 2 aaa batteries last a good 4 month ,and i find that is acceptable , less would be frustrating at least that's my opinion , and the mouse warns you on screen of your mac and with a red led if the batteries need replacing soon which means about within 1- 2 week depending on usage after the first warning
and i have the white silver model , so it fits to my iMac core duo
(they did some more colors too like black silver )
and mine was cheaper then any apple Mouse too , bought it brandnew sealed box for half the price of a mighty mouse ! after over a year usage no complains