I've never had any trouble with Supershuttle and have taken it from John Wayne to DL several times. It will take you to any of the
Disneyland area hotels or inns, and you rarely have to wait long at the airport to catch a shuttle to your hotel. You will generally have around 3 or 4 stops per shuttle, so don't expect to be the first party dropped off. There are several other shuttle companies at the airport, and you might find another company is quicker if you've timed it so that a Supershuttle just left. For that reason, I never prepay. You do have to schedule your pickup from the hotel to the airport, and you might have to wait 15 minutes or so for you return pickup. The only thing I don't like is that you're kinda stuck with that return time. One recent visit, my son woke up sick the last day, and so wasn't up to playing at the parks prior to our flight. We had to check out of the hotel, and DS wanted to wait out the time before our flight at the airport rather than in the hotel lobby. Supershuttle would not take us to the airport early, even though shuttles stopped at the hotel that were not fully booked. We ended up taking a cab.
By the way, a cab is as cheap or even cheaper if you have 4 in your party. With 2, I'd go with the Airporter (if the timing was right that I didn't have to wait long) or Supershuttle; with 3 or 4, I'd go with a cab (no stops, no waits).
I don't think it's ever taken us any more than 1/2 hour, and often a little less.