Re: the comments about business vs leisure and SEA - I'm pretty much strictly a leisure traveler and I have CLEAR. I've found it works pretty well at SEA, which is my home airport. I got it because one day I got to security and the posted wait was TWO HOURS. So I bought it on the spot and was through in less than 15 minutes. I've continued to use it at SEA and have been happy with it. OTOH, my husband does 90% business travel. He doesn't have CLEAR, he has Pre-Check (I don't). The day I bought CLEAR, I was through security at least 15 minutes before he was, but he wasn't in line 2 hours. Other times I've traveled with him, the waits for precheck and CLEAR have been close, but I'm almost always through first. Generally speaking, he doesn't feel he needs CLEAR because he has pre-check.
Can't speak to other airports because SEA is the only one I've departed from that uses it since I purchased it.