I was having issues with Clear when I first joined, I kept getting selected for secondary screening. I have found it better lately. In fact in traveling through Vancouver recently, I found that between Clear / TSA precheck, and Global Entry, I got through Clear for ID check, TSA security screening and US Customs in about 6 minutes, which I think is super quick.
I did wish that they would deal with Clear with TSA Precheck and those with Clear only and NO precheck better. They use of the same machines and same Clear employees, but it is not efficient and it is unclear why they allow one line to proceed while they are holding up the Clear TSA Precheck line (which I am using).