Lots of interesting points brought up here.
True you can get a "good" meter that measures RMS voltage, but for one, they're expensive and most people don't own one. I work with electronics all the time and I don't own one. I just use my scope when working with pulsed outputs. In any case, RMS voltage is not the same as RMS power. With vaping, it's all about the heat so we need to think in terms of power not voltage. My feeling is that with a 3 ohm load, the eGo's PWM output delivers about the same power as a DC voltage around 3.5V. This thread prompted me to a verify my claims with a direct comparison. Using my eGo as a baseline, I adjusted my VV passthru to find the point where vapor output was similar. That point was in the neighborhood of 3.5V. Again, this is with a 3 ohm cartomizer and since we need to think in terms of power, resistance is a factor.
There's always some amount of inefficiency in delivering power to a load. The purely resistive losses can be calculated by multiplying the square of the current with the sum of the internal resistance of the battery, components, and wiring. The higher the current the higher the losses. Comparing a 1.5 ohm load to a 3 ohm load, you'll get four times the power losses in the circuitry. That's why I say that the eGo doesn't handle the load well. It has high resistive losses because of the crappy mosfet, under-gauge circuit boards, and under-gauge wiring.
The eGo battery itself isn't too bad. I tore apart one of my dead battery units to check it out. I calculated a 50 milliohm internal impedance. To give you a comparison, I have a high end 5ah lithium polymer batt I'm using for a project that has a 18 milliohm internal impedance. Just for the hell of it, I did a short test on that eGo battery and it put out 30 amps before it vented.
