So I did in fact get my Waidea this morning. Good delivery times etc.
But first impressions were that it's f'ed

Update: but it might just be that the batteries are completely empty, or dead themselves.. Though if so, it's still been behaving very weirdly (it seems to me.)
- Visually it seemed fine - a couple of little marks here and there, a bit of dirt, but probably would all clean up OK.
- The threads on the ends of the battery tubes (where the caps screw in) seem particularly dirty, but again that might clean up.
- My new Samsung 25Rs also arrived today, and I have no charger, but they showed about 50% charge which should be fine.
- I put my Atlantis on it, asked New Up/Same Down, it read the resistance at 0.55 or something (sounds about right), and it fired OK.
- Then I put my Subtank on it, again it asked New/Same, and read around 0.57. I tried to fire it, and suddenly it read 0.07 and said "Too Low". That's weird, I thought. Maybe I didn't screw it on right..
- I took that off and tried my ELeaf Lemo, which is reading around 1.3. New/Same check. That fired OK.
- Put the subtank back on, it read 0.57 again, then when I went to fire it, the device just shut down. Wouldn't wake up on the fire button 5 times, just nothing happening. Blank screen.
- So I took the batteries out and put them back in, and it woke up.
- But since then, it hasn't ever fired again. It reads the coils and the resistance, and sometimes it seems to show that it's firing - showing a voltage being applied - but the coil never heats up.
- Sometimes it just shuts itself down as soon as you hit fire.
- I've tried plugging it into the USB and pass-through firing, same symptoms.
- When it came it was in temp mode, though obviously was detecting Kanthal. Shortly afterwards I turned temp mode off
- Another symptom: sometimes the battery indicator correctly reads around a half or a bit lower. Sometimes it reads full.
- I've tried it on just one battery, trying both batteries one at a time separately, and tried both tubes independently.
- I've extra-tightened the battery caps in case they were loose or not making a good connection.
- Right now I've left it on USB charging, in case the batteries were so low it's messing it up or something.
Update, here's the most recent test results:
- Tube 1 = the one below the 510; Tube 2 = the one below the screen (that's just how I refer to them)
- Tried four tests: battery 1 in tube 1; battery 2 in tube 1; battery 1 in tube 2; battery 2 in tube 2
- With either battery 1 or battery 2 in tube 2 (below screen), it does not turn on at all
- With either battery 1 or battery 2 in tube 1 (below 510), pressing fire brings up "DNA 40" then it immediately went blank again.
- Then tried both batteries in again, pressing fire brought up "DNA 40" then the screen went blank, then it wouldn't turn on at all.
- Then I plugged it back to USB charge, and the red light is on, battery indicator reads full. I'm going to leave it like that for now.
One problem I have is that the batteries are also brand new, just received this morning at the same time as the flask (not from 3FVape though, UK company), and I have no proper charger yet. So I can't independently check their charge, or charge them up.
I might see if I can go out and buy some different 18650s and a charger this afternoon.
Could it just be that the batteries are basically completely flat?? Or faulty? Certainly the symptoms seem to be changing - like 20 minutes ago the screen would display fully, and it would try to fire, but wouldn't. Now it won't even turn on, or turned on then went off again. This could indicate I was using the very last bit of charge.
But surely it should say "Battery low" or something, not do all this crap?
Anyway not given up hope quite yet, but not been a fun morning so far.