I like CE2 Rev 5 with metal sleeves and my own drip tip (the drip tip does make a big difference for me).
Not the cheapest for sure, and not entirely fill and go easy/trouble free with every juice.
Every once in a while I do get a pack with a bad one in it.
They do last a while however and aren't too hard to totally clean out if you find yourself out of fresh ones and want to change it's flavor. I've gotten weeks out of mine provided I don't insist on trying to flush them out, crack them open, or mod them...but just dedicate one flavor each cart and only clean the coils occasionally. Mainly, I just like the way they vape/taste with my juices and batteries (ego XL) so the little nags about it (ocassional gurgle) are worth it to me.
I've tinkered with them over time and found juices I like that work great with them right out of the box without need for modding and poking at the things. (So far most 50/50 mixes wick great for me...no tinkering or fiddling with the thing).
I do go through more juice with these for some reason. I'm not sure if it's that I like vaping that much more and hit it more often, or if it's really burning that much more juice...maybe a combination of the two.
So...not the cheapest for sure. Some folks HATE these things, while I find it hard to use anything else now...but if you've never tried one before, see if you can get your hands on one to try