I just joined the Clear program as a result of my Hyatt status, and I don't think it's that useful, unless you plan on consistently arriving 30 min prior to your flight. It doesn't shorten the process at all: you still have to remove your laptop, shoes, and jacket...I had thought this process would be shortened as well, but it is only a cut pass, and you end up in the normal UA line at SFO, and people just look at you funny, like you just cut in front of them.

It's quite analogous to the UA Elite line, although it may be useful if you take 6am flights out of SFO, when all security lines are really full.