Bobbi Brown's Gel Eyeliner is a cult favourite by now and although I was (and am) forever hooked on MAC's Fluidlines, I couldn't help it, I had to get it and see how this one compares and performs in general.
I got Green Ivy, a gorgeous darkened green. The texture is more gel than cream, and I found it to be less opaque than the Fluidlines. It is easier to work with, as it's lighter and can be quite buildable; but at times I wish this stuff had a better colour pay-off. I found myself always having to layer it 2-3 times and top it off with an eyeshadow to get that dark, intense line I usually go for.
Overall this is a great eyeliner, it lasts well through the day, it doesn't budge or smudge and even if the colour pay-off isn't that great you can work around it, or just use it for less intense looks. It is a great eyeliner for work let's say, where you want that definition without too much drama.