I've had my share of cocaine experiences and I can tell you there IS a cocaine comedown. You don't notice it if you are preoccupied. Say you're at a party and did a couple lines and continued partying. In that scenario, you wont notice the comedown at all.
But if you're sitting in room alone, and did some lines, I gaurantee you that you'll feel happy, alert, and chatty at first, but then a lot more mellow afterwards. Maybe comedown is the wrong terminology. But when your mind suddenly changes from chatty to normal again, we interpret it as a comedown due to the change in state of mind.
Ashley posted a wonderful quote in TDS, and I think it portrays my view quite well:
"There are as many nights as days, and the one is just as long as the other in the year's course. Even a happy life cannot be without a measure of darkness, and the word 'happy' would lose its meaning if it were not balanced by sadness." -- Carl Jung
The cocaine "high" is merely a change in our state of mind. If your mind never returns back to baseline, then we would never be able to get high again.
But anyhow, I do agree that cocaine is one of the softest drugs out there. Short lasting, great feeling, and barely noticeable comedowns.