This is my favorite liquid eyeliner I have ever tried. It does have its flaws, but for my purposes I've never found anything better and I don't find the need to go looking for a different option.
Perhaps my favorite feature of this liner is the brush tip. I got a KVD tattoo liner sample one time and enjoyed the tip a lot, but I wanted a drugstore option. This has the same kind of brush tip that makes it super easy to get a thin, precise line. I've had a few years of practice now, but even when I was a beginner this made winged eyeliner super easy compared to felt tips. The tip is spring-loaded, so if you're running dry a bit, you can pop it in the cap and pump a few times and that usually makes it nice and juicy again. Also, this is a minor thing with the packaging, but the shiny silver makes it really easy to find in my bag amongst dozens of similar sizes black brush handles/eyeliners/etc, which I appreciate a lot.
The issues really come up with the formula of this. My biggest gripe is the staying power. If I have a normal day and don't touch my eyes or anything, this lasts just fine without smudging. However, if my eyes are watery or I take a nap, this pretty much doesn't stand a chance. It doesn't run or smudge all over your face, it just kind of disappears or flakes away. This does layer well on itself though, so if it does end up coming off it's an easy fix. If nothing messes the liner up, it can last a full 12-14 hour day without any issue. Another thing, this definitely needs some kind of powder base to stick to. If you try and put this on a bare lid or just a cream shadow, it isn't able to layer to get the right intensity. It's like it has a hard time sticking to the skin. So if you like to wear just liner without shadow, I'd suggest putting down a skin tone powder on the lid before applying.
Overall, this is a really good drugstore liner if you prefer brush tip pens. It's not perfect, but it gets the job done and the positive outweigh the slight negatives.