I recently started with clipless (Crank Candy 3s) and they did take some getting used to. If you plan to get them for a mid-September ride, I would recommend getting them ASAP and riding with them as much as you possibly can before the long ride. For me, it's not the clipless pedaling that takes some getting used to -- that part is easy (and does seem more efficient). It's the clipping in and out. Personally, I would want to be comfortable with sudden starts and stops -- & handling unexpected jostling if I were planning a group ride.