It's solidly built, has a long battery life, has both 510/ego threading, fits easily and nicely on ones hand and pockets. It is a little bit heavier than an ego style battery, but it is completely metal (except for screen and firing button), and can withstand punishment more than some other devices. It is compact, easily portable and can be used as a passthru or personal charging station (in fact, during severe weather many vapers have reported using it as such to keep their phones alive when they are without power).
You can use any juice delivery device with it, and it delivers a more powerful vape than even a spinner. It also has a nice indicator in the firing button (Green, Yellow, Red) to let you know when your battery is depleting. 2600 mAh battery = 2.5 days for a lot of people.
If you wish to stay in the form factor of an ego-style, look into the Itaste VV V3, which is a squarish 800 mAh ego style with VV and VW, and a micro-usb to use to charge or passthru.