I have used cocaine many times in my life. I'll explain the effects (to me at least) to the best of my ability.
When I blow a line, the drip starts nearly instantaneously. I feel it go down my throat and my tongue begins to numb. The effects onset after about 30-60 seconds. I feel euphoria, talkative, happy, and ready for anything. I just talk and talk and talk. I sometimes experience slight shakiness, tingles in my head, and an overall sense of pleasure and well being. The effects last around an hour, and then I feel tired and a little worn.
The quality does indeed affect the high as you can likely imagine. There's no way to tell how pure it is, but some coke is heavily cut and some is more pure. If you haven't experienced what I've described, it may not be very potent. Stay safe. I hope I've provided insight. Cheers.
keldon