I have an obsession with eyeliner as well and I have zero cons with this. I have oily skin and the eyeliner (in my 5 months of having it) has never creased or transferred for me. The color is pigmented and you're able to go over the line without worrying about the color flaking off. The pen is very very easy to use and the brush tip (I can't stand felt tips) makes the product glide on very well. It's my forever go to. I can do a cat eye in like 30 seconds with this. 10/10 would recommend.
I was really hesitant about buying this product. I believe Its like 15$ at Sephora. Why buy 15$ eyeliner when I can buy 6$ eyeliner @ a brugstore? well my friend talked me into it and I've been using it since December. I love it. the felt tip makes it so easy to use and apply. It also lasts!! I love this.