I love this eyeliner so much! I have been using (and repurchasing) it for about 2 years now.
I love it because the shape makes it super easy to draw a perfect line across your lids and the pen is also quite thin so you can control it easier. Another benefit is that it really truly does last the whole day.
Before this I used the Maybelline Master Precise - which is very similar just a bit thinner - but I had to change because the master precise was not drawing properly overtop my more thick eyeshadows (think Mac or Maybelline paint pots). This Stila eyeliner applies perfectly over both thin and thicker eyelid colours without damaging the pen and so that makes it a win for me.
I think this eyeliner is one of the best in the market.
It is so black and applies really well. The pen itself isn't very dry so makes application easy where you don't have to keep going over the area to make it darker.
It was recommended to me by one of the girls and Mecca and I'm glad I purchased it as I do reach for it very often and over my other eyeliners