VW is a cool feature, but only if you're using different delivery devices with different ohms, as has been previously stated. All of my cartos are low-resistance 2.0 ohms, so I really don't have to mess with VW. I know my sweet spot is at 3.8 volts. The only time I fiddle with VW is if I'm using something around the 2.5/6 ohm range, and only several of my delivery devices are at that resistance. ::shrugs shoulders:: I'm a low-voltage vaper.
VW is a cool feature, but it's just a feature. Sort of like puff counters. Cool, but not necessary. Baditude was right, any smart vaper will know where their sweet spot is, depending on the knowledge of ohm resistance. I suck at math, and it's not that hard. 2 ohms and you're ok between 3.7 and 4.2 volts. And for me, 4.2 is pushing it (my cousin vapes at 5.5 volts with 3.3 ohm cartos -- that's WAAAAY to high for me).