I'm actually vaping on a v4 as I type.
I got a v1 right when they came out (still vaping, .4ohm twisted) a v3 about two weeks ago when they first starting appearing on ebay (absolute perfection, .5ohm macro coils) and now i have two of these v4s.
they each have their issues, but each share the same core strength: ridiculously great vapor production, airflow, and flavor. oh, and they drink juice like a highschool kid at a kegger.
my impressions so far:
orchid v1: introduced me to an entire new world of vaping bliss. dropped my kayfuns, nautilus, and even my drippers. this became my main, and my fogger 4.1 and 4.4 became my backups. but oh my god how i hate those screws. mine came with the ULTRA weak hex screws that all stripped instantly. I struggle to get the thing built and STAY built. I finally took to twisting 26 gauge kanthal just to give the screws something to bite into. this build works alright, so long as i'm gentle when changing out wicks. vapes like a dream, just a complete pain to maintain. I replaced the top cap with that fasttech top-fill, which greatly enhanced the overall usability.
orchid v3: WOW. it's amazing what REAL ACTUAL SCREWS can do for an atomizer. this thing is rock solid. i've put several different builds on it, not because it needed rebuilding, but just because it's a joy to rebuild on after weeks of struggling with my v1 (not to mention my foggers. who the hell builds an atty without post holes??). capacity is about .3 ml less than the v1 (thanks to the inner structure of the included "nano" style tank) but i don't notice. i fill up all my orchids once a day anyway, so it's fine. everything else about the vape is identical, and therefore amazing. this is what vaping heaven is like.
orchid v4: ok, so. the v4 is ostensibly just the v3 but with a longer chimney stem and tank, and therefore enhanced capacity. right now, i have no idea if that's actually true, because every time i try to fill this thing it leaks half the juice i put it, seemingly. It's got the bottom-fill port like the v3, but while the v3 is dead-simple to fill kayfun style, this thing seems to HATE taking juice into its precious interior. first i get killer backflow, like top-filling the v1. so i go slow, fine. but then it starts gushing out of the tip (holding it upsidedown). and i notice that the juice seems to sorta bunch up around the rim of the chimney, where it narrows down to the stem part. it's almost like there's a chokepoint and the juice can't really get past there. and in fact, as i hold up the v3 and v4, both half-filled, it really does look like the chimney on the v4 is closer to the PC window on the v4 than on the v4, so maybe there actually IS a chokepoint. the vape is still amazing, and if I can figure out how to actually fill this thing, it might be perfect. But i was expecting all the ease of the v3 (yep) with just capacity boost (yep) and no additional problems (oops).
so.
right now, the v3 is actually my favorite out of all these orchids. as soon as i finish off this half-tank in the v4, i'll try another fill method. I just opened my second v4 and measured the capacity using water. water via a syringe went into the bottom just fine, and it took almost 5.5 ml (!!) before overflowing. for giggles i went ahead and did the oldschool v1/kayfun topfill method and it took 5ml like a champ, so long as i covered both airholes while i filled. pretty dang impressive. if i can get the other v4 working perfectly (i really really hope i dont have to topfill) then I'll go head and build the second v4 and retire the v1. i think the v3 is sticking around for good though. old reliable now (two whole weeks, lol).
I will update as appropriate.
EDIT: i forgot to mention that the screws on the v3 and v4 are Philips-head, not hex. the spares for the v3 are also Philips, but the spares for both of my v4s are actually hex. so I guess i'll have to be good to these screws so i don't have to go back to the nightmare-fuel hex screws.