Yeah, version 4 sucked and I haven't tried version 5 because I'm not hearing great things about it. I admit that the wall around the juice well in the mini v3 could be considered problematic, but I actually prefer it over the old kayfuns where you had try and keep the wick from getting snagged and in staying in position when putting the atomizer chamber back on.
The big improvements in the mini v3 were eliminating the whistling so that you're not calling every dog in the neighborhood, top filling, the ability to remove the deck and re-wick it with the juice still in the tank, and the juice shut off so that you can store it in your case without leaking issues. I even preferred the smaller amount of juice it held. The only reason I switched to the plus version was asthetics. I thought the wider tank looked better on my provari.