I suggest until the R4 is in everyones hands that when you recieve any version from r3.5 and below the first thing that should be done is to dry burn it to ensure there is nothing left on the wick.
this will ensure a better taste since you wont be puffing through a wick that has primer on it.
im seeing many people are receiving the lower ohmed verison 510's e2.
that will get a metalic chemical taste, its not really a chemical taste though, this happens when i pump up the voltage, so 2 things, either a lower volt is needed like a riva,ego,hello or a variable device that goes below 3.2 volts.
or you need to use a higher ohmed e2 which the 808 xl e2 are and the new r4 which comes in higher ohms up to 3.2 ohms which will work fine at 3.7 and above and below.
To get it to WORK RIGHT NOW on a 3.7 device then I suggest people take the few minutes it takes to watch the vid and do the ptb method, the reward is greater then the risk.
it solves all issues for me, no leaking and super wicking.
once ptb's you can take 1 second drags and gets huge vapor or take longer drags for intense action.