That looks like a very interesting "mod". It should work similar to other eGo units and be compatible with "eGo Stuff". That said, if you aren't worried about backward compatibility, you should consider the same things for this that you would consider for other mods:
1) Do you use, or plan to use, Dual Coil (DC) cartos? They need lots of amps, and generally AW IMR batteries. I don't know the specs on this mod to know its max-amps. The PWM regulated voltage appears to be similar to existing eGo stuff (3.4v).
2) Do you want full 3.7 volts (like directly off battery voltage)? The all-mechanical mods do this without voltage drops due to switches. They have "fat buttons" tho.
Overall, I think that this is a neat unit, since the eGo charger will charge the battery inside the unit (charger built into circuitry) so you just screw it in like you would a standard eGo. Thus, you don't need a separate charger if you already have the proper eGo USB charger (verify that it is the correct one). I'd probably have an external charger anyway, so I could just switch batteries and not have to have another PV for vaping while this was charging.
The prices looks reasonable too. And you can get parts separately...switch, tube.
The e-power, for example, is higher voltage (follows battery voltage less any mosfet drop ...I think..last I heard.) It doesn't charge in-unit so you need an external charger. Same with the all-mechanical mods: battery-voltage and external charger.
Overall, I like the fact that you can replace the battery, or have a stack of charged batteries around and just swap the battery without having to carry several units. Particularly if you have "eGo Stuff" and want that eGo specific connector.