It's been a month since I first received the preproduction batt, atty and two tanks. Since I've gotten kits from cignot, tanks from TW and attys and tanks from heaven gifts. I'm finding no difference except as noted - the preproduction atty had a slightly narrower spike. I've had no leaking problems with the tank in the atty. I had one tank that I prefilled and I failed to put the rubber on correctly - aligning the air channels with the bumps on the rubber and had a leak onto a table... but again, not 'in the atty'. I have not cleaned any atty yet. I have 6 going. I use a DIY Decadent Vapours ejuice using the VG Platinum Ice nic base, Aqueour Glycerine (80:20 VG:H20) and the flavoring to around 11mg nic. I have tried straight PG and a PG/VG 75/25% mix and found no difference in vaping - no clogging - good draw etc. (the draw on SE Riva's - see below- is tighter than the old Rivas, Tornado and eGos but that is more of a batt thing....). 
Taking off the cap to fill isn't a good plan, imo. The one where I did that - the top looks pretty ratty although it still hasn't leaked. If you do - make sure you align the flat sides of the cap to the flat area on the tank. 
I've tried to find a way not to use a syringe or needle tip bottle - although I do have one flavor in a needle tip bottle. The best way of filling for me has been using a small 3inch pipette. The tip is small enough to get into the hole - although I have 'reamed' the hole with scissors - careful not to go too large. As long as their is space enough to let the air out - all is fine. Cignot's 30 ml bottle tops are fine funnel tips and they work as long as you don't plug the hole entirely. 
Flavor for me has been as good as dripping and better than any other cart/carto/E2/etc. with no off flavors. Also the 1.2-1.5ml - I fill to the top - gets used up faster than any other device. The cylinder mega eGo attys have the longest vape time still. But the tanks are better/longer in time than any regular 510 cart or carto by far. 
One 'development' is the new SE Riva's (liberty flights is where I got mine) according to Scottbee's underload testing (thanks Scott) are putting out more voltage than regular "TorneGos" and this results in a 'near Bartleby' (for me) true 3.7v box mod type experience. Even more vapor and flavor (although some flavors respond better to more heat than others - so 801/cool vape/& fruit and berry fans won't like this as much... etc. etc. ). However..... the SE Riva threads one the ones I have don't work well with the cignot tank attys - misalignment - although I gently forced one to work. The heaven gifts tank attys take the SE threads better. And one other thing - off topic to the tank system - I had one SE Riva that wouldn't fully charge (light stayed red) on a TW charger although it worked well on the charger than came in the SE kit. Scott also had a charger problem with one of his SE batts....
With the Tank system batts from cignot - there is a 'rhythm' to get the battery lock to work - it's quicker than you'd think - 5 quick presses where the light doesn't really go off in between pushes - at least that's what I've found works. Same with 'unlocking' - 5 quick presses.
I've 'retired' my last Bartleby - significant for those who know me - and the last wetbox as well. I still have a big brother set at 6+ volts - which I find does best for my 'BWB espresso/capp. coffee PV'. So with that exception I'm fully 'tanked' 
