I flew SFO-ORD on the 6:10am flight yesterday (10/10)... I was at the airport by 4:35am with no bags to check. The line moved pretty fast past the UA ticket-checker (you show your ID and that day's itin and they let you through to security) and security itself was moving OK-- one person helping feed bags onto the scanner, two people watching the scanner, and about three or four people "wanding" people once they passed through. I'd say that from curbside to just inside security was 10 minutes (including the stop to have my nail clipper confiscated).

The longest line I saw: the 30 of us waiting outside the RCC at 4:45am to get into the club--opens at 5am.