I have three of the vv rivas. With two of them, the battery center post is slightly off spec - iow, emdcc's, eGo-t and c tanks and a cisco 306lr need to have their center posts picked and heightened to get a connection. The other vv riva works just fine on all connections. And when the centerposts of the attys are raised, the other two perform well.
One thing on charging - is that one (and now I'm not sure which one

fully charges to where the 5 leds stop blinking, whereas the other two don't give the final 'done' indication and keep on blinking - and I've let them go way past the time where they should be fully charged. so when it's down to the last led blinking, I'll pull them off the charger. That said, I don't think they are 'less charged' - only that they don't give the final indication. They're rated at 650mAh iirc, and they do seem to last a bit longer than the 650mAh eGos.
The change in voltage, imo, is noticeable on flavors, esp. on the eGo-c and even at 4.2v (actually @3.9v underload) I get no burning or discoloration with the ejuice (as happens with the t's at that voltage) But... it will still wash out taste in lighter flavors but again, without burning them on the c's.
That said,
for most flavors, I'm liking the eGo t or eGo-c batts best (eGo-c is supposed to be 3.5v underload vs. 3.2-3.4v for the regular or eGo-t batts). The exception is my 'coffee' vape - DV's Doppio Espresso, BWB Espresso and Capp. 2 drops each dripping on a cisco 306lr - and those ejuices, for me, need the 4.2v setting. I also have a PT vv which I run the cisco on, but on vacation I'll be taking two of the regular vv rivas along for coffee. So at home, I basically don't need the other three although I use them on occasion. The eGo-c changing button led to indicate charge is a nice new feature - it's more exact on the vv's leds but sufficient to know you're not going out with an eGo batt that is almost out of charge - as long as the eGo-c batt is 'in the white' you have a good charge left in the batt.
Function-wise - other than the initial short spec on the centerpost and the charging thing - the vv's have performed well and as expected, but with the new eGo-c batt with the charge indicators, I have no need for the vvs other than for the coffee vape and if you have strong flavors, I'd highly recommend it - in fact, I'm considering selling my big brother vv because that was my 'coffee pv' before the vv eGo PT and that is doing the job.
I should mention that I've had the PT since they were released and the regular vv rivas from LF shortly after they began selling them - iirc over 2 months ago....