I recently purchased a Visor deluxe (love it!) and called Handspring (at 5:30 a.m. California time no less) to ask about using rechargeables. The helpful operator said that it is OK as long as you do not let them run out completely as NiMH batteries will cut out at once thus not giving the system time to back up data. This could result in the loss of all data. Apparently, alkaline batteries die a slow death so the system knows to back up. Anyway, as long as you recharge the batteries before they die you should be OK.