I personally love the tank for its convenience for on the go and pure lazyness when its working properly.
Awesome vapor production and good throat hit for those that like T.H.
It is a great start for a new technology/method but far from perfected hence the different atty models/versions/revisions.
That being said, I also hate it for the small and annoying traits it has.
Flavor is diminished, not majorly but comparatively opposed to other systems/methods.
Wicking, can be annoying if your using too thick of juice or if the wick is not at its optimal depth/position.
Battery and atty contact, contact points are made with very small tolerance and as these are made by the thousands there are inconsistencies as to the precise depth and contact when screwed together(easily fixed by using a small pointed object or tweezers and either lifting battery centre post up or wiggling atty centre post down. Battery post is usually depressed when screwed all the way into charger, this is unnecessary, when screwing battery into charger, stop screwing when battery button light starts to flash or charger light goes from green to red, at this point contact is made and charging has started so continuing to screw the battery in only pushes the battery post down into the battery sometimes causing battery and atty connection issues when next used after charging.
Airlocks/hydraulic locks, pulling the cart out often and allowing air into the cart helps wicking as it prevents the airlock and wicks better preventing dry vapes(nasty!)
Leaks, yes, several factors, from leaking into the battery, leaking into the bottom of the attys cone, to "leaking" into the mouthpiece.
All can be fixed but requires patience and some experience as to how it is used.
Leaks into battery i find can be fixed by adjusting the height of the wick and using thicker juice, and sometime a good wash with hot water seems to work too.
Leaks into mouthpiece can be fixed by not drawing as hard and popping the tank cart out every 5-10 puffs and wiping the moisture off the outside of the cart, along with removing both inserts(on mouthpiece of cart) that restrict airflow and "prevent" juice from entering your mouth. Also when finishing your drag, continue to draw once you've let go of the button to clear the chamber as this vapor left in will collect on the walls of the cone and cartridge causing a diminished flavor/vapor next use along with a possible bit of it being sucked into the channels on the sides of the carts into the mouthpiece and then your mouth.
Leaks into the atty base/cone, hmm, still scratching my head on this one, only does it on one of my attys, almost like when the cart seats itself on the needle it open the hole to much and spills over the side, can be fixed by adjusting the depth of the entire atty insert which is press fitted into the cone. This is also a possible reason as why juice is leaked into battery as sometimes a atty's press fit tolerance is not enough and it can be loose allowing juice to seep though.
Some atty are perfect from the manufacturer but few and far between.
I find its a matter of getting to know the difference between the attys you have for it as each one is a little different, ie. some i draw harder on, some less, some i can draw immediately on, some i wait 1-2 secs after firing battery for the coil to heat up as each attys coil seems to operate slightly different as to how long it takes to "glow" and produce nice vapor(noted when doing dry burns after cleaning)
Overall, i still like the tank system regardless of the problems. I look forward to a few more revisions that should address these issues in the future. This post/info is based on my experience of using a tank system for almost 2 months now and i am still getting the kinks worked out as to how to make this system work better for me. Others might have different experiences and info but this is what i know to be true for me.
This system has got me off analogs 100% the first day and for that it is worth every minute of hassle i have had to deal with it. I use it with 50/50 PG/VG or 20/80 PG/VG, i prefer VG, PG is too much for my throat/lungs/mouth. And all my juices/flavors i use in it have menthol added as i like the "coolness" and find it buffers the vapor irritation nicely to where i can chain vape all day long.
As for maintenance, i get 1-2 weeks out of a atty before i rinse with hot water, dry, and then do a couple quick dry burns, this will vary due to types of juices used(dark, sweet, etc).
Battery life, on my 650 mAh, from morning till afternoon/evening, then change.
On the 1300 mAh i get almost two days worth depending on use.
Would i recommend it, yes, is it perfect, hell no, but it works for me.
Its one of those you either hate it or love it designs that will require some fiddling with at one point of use.
Hope you find some of my input useful and find a system that works for you.
Good luck.