I already also heard, that the batteries are a bit more than 1.5V, maybe 1.6V or 1.7V. A new "1.5V"-battery I measured had a bit more than1.6Volts. That means that 1.6V*3=4.8V should be definitely still in the acceptable range for the laserpointer. Most of them are from China and hence don't have a manual with technical parameters.
I recall last year in the camera forums, people were shouting about using the new NiZn batteries because it sped up their flash recharge times, and then about 6 months later reality set in, when it became apparent that some/all flashes weren't prepared for the higher voltage. And if you mentioned using NiZn batteries, manufacturers might not honor warranties (http://strobist.blogspot.com/2011/01/nizn-batteries-long-term-update.html).