I haven't noticed any difference with the type of batteries in my Magellan . . . but then again it's a Magellan (sorry fellow Magellan users, I just have to get the digs in before Hiram can! )
In all seriousness the only thing I've noticed with rechargeables is that when the low battery alarm appears it means the unit will be shutting down in the next couple of minutes whereas alkalines usually give me several more minutes of use before the unit shuts itself off.
"Courage is not the absence of fear, but the realization that there is something more important than fear."
"Death is only one of many ways to die."