For those of you who are really serious about wanting one PV that will replace all others and of course is variable volt, then the Darwin truely is that PV. There is no other PV with a built in microprocessor that automatically adjusts the wattage of the unit based on the change in the resistence of the atomizer or cartomizer. It really provides the ultimate in consistency over as long as you are vaping. No need for any other batteries either since it uses polymer batteries that are internal with a 1 year warranty. And the complete PV comes with a 2 year warranty. Have you seen that in any other PV, ever? I haven't. Plus it is so simple to use that someone who had never vaped before could use it out of the box and just about forget about it.