I will agree with the aspect of less time between refills as the typical kanger carto holds 1mL and the CE2s hold around 1.8ish mL. Once you get the hang of the modifications they aren't that much of a hassle. I personally do the modification where you remove the lower cup seal, flip over the middle o-ring seal, stick another o-ring seal in there for spacing, and then stick on a drip tip. I did not say it was rocket science, but there is a certain aspect of fiddling with the unit to get it to work properly so there is a slight learning curve with these units (and a little bit more when you get into the cleaning/dry burning). I view filling the typical 808 filler carto and CE2 as about the same amount of work. Your comment about the leaking is good to note, since the CE2s often drop liquid out of the center which can royally screw up a KR808 auto battery.
Since the original poster is asking for advice to make an educated purchase, I felt it was important to point out that these units are not less fuss compared to the drip to fill regular style kr808 cartos. Not rocket science, but definitely not less fuss.