Thought I would add my own, very subjective, thoughts to this thread.
My main point of reference for this review is the Storm (with the upgraded free-flowing glass mouthpiece), which I used for about two years.
The Storm is an excellent vape at an amazing price. The only real downsides to it for me are the form factor (not pocket-friendly) and the way the rubber mouthpiece push-fits into the body of the vape.
IMO the V5 Nano is a good budget vape. It's the ideal size and form factor for me (fits in your hand), although the way the mouthpiece is removed and stowed in the body is not to my personal preference.
There is just about enough airflow for my taste - I hate the asthmatic feel I get from too much draw resistance (like from the Fog or the version of the Storm with the black mouthpiece). As already mentioned, my previous vape was a Storm which had really terrific airflow. Some users have reported that the glass mouthpiece gets too hot; this isn't an issue to me though. It certainly gets warm but not too hot for comfort.
I like the high resolution LED display although it's a tad bright. Being able to see the exact temperature is a feature I like a lot.
Dialling in the temperature is simple and the chamber heats up nice and quickly. I set it to 200C for most of the time but if the herb is dry (like from the bottom of the bag) it can start to smoke - so I dial it down to 190C.
After a 10 minute session, you have to blow bits of vaped bud from the mouthpiece screen while the vape is still warm otherwise the bits get stuck and interfere with airflow on the next session. But that's the only cleaning you need to do before the next session.
The black ceramic chamber is great. The Storm had a white ceramic chamber which got dirty very quickly and was hard to clean. But that dirt didn't build up much; it just looked a bit messy. The chamber on the Nano, seems to actually repel gunk. It's not just that the blackness of the chamber makes the crud less visible, it just doesn't get as dirty. I only cleaned the chamber for the first time after about three months of daily use. Overall a stainless steel chamber may be better from a cleaning point of view, but the black ceramic is absolutely good enough for me.
Battery life is fine - I get about 30 minutes use out of a two-year-old heavily-used Samsung 18650. Haven't tried it with a new battery.
The plastic flap on the base (to access the stored mouthpiece and battery) is a little fiddly to open/close and seems rather breakable. In fact the catch on mine has broken (more on this later). The metal battery cover has a flimsy feel that does not bode well. And if you accidentally close the battery cover without a battery in there (something I've done once or twice) it feels like the cover might break. That said, the battery cover has not, in fact, broken.
Cleaning the mouthpiece assembly is OK and is something I do about once a week (I generally vape for 3 ten minute sessions minutes per day). It's comprised of a glass mouthpiece, plastic (I think) base (into which the glass mouthpiece pushes), a stainless steel screen, rubber retaining ring (keeps the screen from falling out) and two tiny silicone grommets (to help the glass mouthpiece form a seal with the base). All this comes apart easily except for the two tiny silicone grommets. Just dump everything in a bowl of isopropyl alcohol, swill it around for a few minutes then give all the parts a wipe down. My only real reservation about this is that the iso will eventually rot the rubber and silicone - and these are not available as spare parts. But a new mouthpiece only costs ~ £12.
I mentioned that the catch broke on the bottom flap/cover. I reported this directly to Flowermate and I regret that I have found their customer support to be lacking. I logged the fault then had to wait nearly two weeks for a reply. I was asked to provide more information which I duly did the following day. Nearly another two weeks have passed and I have yet to receive a reply to say that a warranty repair has been approved or not. So nearly a month since my initial report and I am no further forward. This could well deter me from purchasing another vape from Flowermate.
So, as far as the product is concerned, I have to say that, overall, I'm pretty happy. The thing which I liked least about the Storm was its form factor; pretty much everything else about it was great. The Nano is nearly as good BUT the form factor means that I use the Nano almost exclusively.
Shame about the customer support.
Still looking for the perfect vape. The Davinci Miqro looks interesting . . .
Incidentally, I wish that vape makers would make a point of offering cases with their devices. The Nano came with a pouch, but this offers no protection at all. This case is a bit tight, but it does just about fit:
https://www.amazon.co.uk/gp/product/B013ESF7SE