I'm really late to the game here, but hey, I just got mine yesterday. So I won't waste time with any semblance of an exhaustive review, just a few comments.
Pros:
At least so far, button clicks register very consistently. Once I figured out that it's 4, not 5, clicks required -- doh. Unlike some of my other ego batteries, which seem to have a different interpretation of 5 clicks than I do, and thus require several attempts to power them on or off.
I don't have a volt meter, but the different voltage settings seem to be in the ballpark of what I'd expect. So far I've only used it with a Stardust with 2.4 ohm head, and find the 3.6V setting just about right. 4.2V feels too high, but I'm not into "awesome" throat hits and hot vapor. But I'll try the higher voltages with a 2.8 ohm head when I get a chance.
Cons:
First and foremost, the size. I've got fairly small hands for a guy, but this thing feels really awkwardly tiny to hold, and I hate the low placement of the button. I get the novelty and the "cute factor" of such a small device, but that aside I can't imagine even the daintiest of hands having an issue if it were, say, half an inch longer. And I could see the small size being a plus for stealth vaping if this were portable, but for a dedicated passthru...??
Length of the USB cord (or lack thereof) -- somebody posted here just yesterday that it was a generous length compared to some others. Huh? I've got it plugged into a USB adapter which is plugged into the power strip sitting on the floor smack up to the side of my desk, yet the cord is so short that I have to hunch down toward the power strip to take a toot, it doesn't reach my mouth when I'm sitting upright. I wasn't too concerned about the well-documented iffy-ness of the non-reinforced connection of the cord to the battery, since I'm fairly gentle with my toys, but now I am -- I'm too likely to put undue stress on it just because it's so flipping short.
Long story short (didn't mean to blather on so much)... I think I'd really like this if only both the battery and the cord were just a wee bit longer.