That taste May go away. Most cartos I've used have a taste upon start-up that Does go away-usually within a half-tank.
I don't think filler "tastes", I think there's some residue leftover from the production of it or maybe washing it to clean.
It's probably a matter of taste bud sensitivity. I'm one of those annoying people that can taste and smell things no one else can. Probably why I dabble with gourmet cooking and am always fiddling with perfecting cocktails, growing my own vegetables and herbs, etc. I really do notice very slight nuances in flavor and aroma.
I've tried a number of ways to get e-juice to the coil in my first two months (almost) of vaping and I know that for me, the ideal flavor experience is the one that eliminates wicking material as much as possible. My best vape has been just dripping into an atomizer. But there's no way I am going to sit and drip three drops at a time into a metal tube. It's not time efficient and it's not aesthetically all that appealing.
Please someone, invent a pretty bottom feeder. I will market them for you and we'll be rich! ;o)