I have had mine for about 3 days, overall I like it.
I am using mostly rebuildables, it will fire my 1.5 ohm with no issue but my .9 ohm gen causes an error. The ohm limit is in between that somewhere.
From what I can tell this not a PWM device, if it is they did a good job of hiding it. I get no pulsing/vibration noise and the voltage seems pretty accurate to me, maybe a little higher then the setting but not by much. Certainly nothing like the Smoktech VV Gripper.
The 40 C "limit" doesn't seem to exist, I think something got lost in translation here. It displays a "high temp" icon when the temp of the control head hits 40 C but it keeps firing. I ran my temp up to 45 C before laying off it. I have only experienced this when using while charging. Of course now that I typed it, I just paused to vape and it showed up while not plugged in.

Seems to do this when the voltage setting is above 4.5 and chain vaping.
For a quick little non-scientific test of the amp limit, firing a 2.0 ohm Single Boge Carto and it does seems to run 3.0v to 5.0v without hitting an amp limit. Using the only 3.0 ohm cartos I have, left over Blu's, are the same. My single 1.5 ohm stuff runs into a wall around 4.5v. This seems to be pretty close to a 3 amp limit. I do not have any functioning dual coil setups to test at the moment.
I also have experienced nothing happen when plugging it into my PC problem. Reinstalling without uninstalling the MVR software seems to correct it and maintain the record. I have had to do this twice already.
I'm not sure if it's a mind game, but the battery seems to charge really quickly compared to my other 18650's which are smaller capacity? Not sure why this would be, the battery does last much longer than my others. I think I maybe perceiving it charging faster because of the display showing the percentage charged. Perhaps others are experiencing this ?
It is interesting to note, I did notice that the puff remaining count changes as soon as a new device is screwed on. I have not figured out the VW settings as of yet but it does not seem to adjust voltage to match a watt setting unless you enter the Power Set\Output menu. This leads me to believe this could be changed with a software update.
That's my experience so far, I hope it clears up some of the questions that are popping up in the thread.
If you can read German or have Chrome read this:
Joyetech eVic: VV Akkuträger mit PC Anschluß » Mountain Prophet