I found I had to layer up the colour a bit to get a properly opaque black look and due to the nib being so thin I had to do a bit of 'colouring in' to do a thick line (my go-to eye liner look), unlike with a brush applicator when you can just paint it in quickly.
I also noticed a more significant down side that for me is a bit of a let down. When I drew on my line extra thick and wore it for a few hours I found that after a while a shadow formed on the upper part of my lid where the line had been touching whilst my eyes were open. It's not easy to wipe away either, it's sort of like the shadow you get under your eyes if your mascara or eyeliner has the same tendency. If you only use eyeliner for thin lines then this isn't going to be a problem for you but for me, who mainly wear thick lines this is pretty big problem. I think the way I'm going to try and overcome it is by doing the main bulk of the line in a waterproof eyeliner and then the flicks I'll do with this. I also found it really hard to remove without a lot of rubbing which I really don't like doing.
So, all in all:
- quick drying
- reasonable price
- packaging looks good
- good for precision and detailing
- leaves a shadow
- needs layering to look opaque
- difficult to remove
They also have a really cool website with suggestions on how to use it and different looks, I'd check it out just for general eyeliner inspiration.