I've had a few differente experiences with them. Not from/to LGB though.
From ONT, we left quickly, but then circled back around and did another slow drive by of the terminal. No one else needed his services so we were the only ones in the shuttle.
From SNA, I got in and waited a short while, one other person needed the shuttle, and we left quickly (no driving around). The other passenger was staying at the hotel next door to mine so that was fast.
And after the ladies trip, I took SS back to LAX...they wanted me on board 3 hours pre-flight, and I was the first on...we spent an hour driving up and down Harbor picking up pre-arranged passengers at hotels. NOw it was OK b/c everyone was happy and joyous and chatty!
So those are my experiences with supershuttle.