No you don't have to take the carto apart to refill it, it's really easy but it takes some time to know when you have to refill it (by squeezing a little bottle for mine). I recently bought a vmod and i love it, but you know that's really different than a device looking more like a cigarette. I use a 808 when i'm outside, and the vmod at home!
You can also use atomizers with the bottom feeders devices, and IMHO it gives better flavors than carto.
Well i'm not an expert, so i hope people with more experience than me will agree or disagree with what i'm saying!