I bought this in white, so I can't comment on the quality of the other colors. But if you're looking for an opaque, long-lasting white gel eyeliner that wears comfortably, this is a great option.
I've used this with a brush that wasn't that great for doing eyeliner, but the thickness of this product made it really easy to control and place precisely. I imagine with a proper brush this would be super easy to use. I initially bought this for a concert, and I put the liner over a very bright pink/purple/blue eyeshadow look. The colors bled into the white a bit on the first layer (which I expected, considering they were shadows from the UD electric palette), but a second layer gave me a completely white, opaque wing. I imagine you could use this over a more neutral look and get away with just one layer. I really enjoyed how comfortable the liner is. I've used the NYX Vivid Brights liquid liner and that dries down to a very tight, dry finish that you can feel every time you blink and starts to crack after a while. This gel liner was pretty flexible and comfortable, and even though I used a few layers there was no cracking.
The staying power on this product is the real selling point, though. When I was applying it at first, I wiped the excess product from the brush onto my hand. I had liner on my hand until about 30 hours later- it withstood hand washing, showers, dishwashing... you name it. I even tried to scratch/scrape it off and it held tight. It did well on the eye too. I applied the liner around 3PM. I was sweating throughout the whole concert and my eyes were watering at some points from the false lashes, this didn't budge at all. I was lazy and didn't wash my makeup off and woke up the next morning around 10AM to still-perfect eyeliner. It is a bit difficult to remove with just face wash, but I used a cleansing oil and it came off pretty easily.
I'm probably never going to use the whole container, but if I somehow manage to and need another white gel liner, I would buy this in a heartbeat. It performs just as well as any high-end liner I have used (if not even better) for a fraction of the price.