Secondly they take a bit of getting used to,
Like ski bindings, your shoes are held by a sprung mechanism. Everyone will tell you when you are new to clipless that you will fall. I can tell you it's true, it is almost always a zero speed fall. When you stop, and you haven’t unclipped the foot from the pedal you are left on the ground or in the hedge with the feet stuck in the pedals. Every cyclist I know has experienced this rite of passage.
The things to remember is that your feet do not have to be locked in for you to start pedalling you can put one foot in, and rest the other on top of the pedal, getting a bit of speed and make sure you have a bit of road or pavements ahead, (not fence) before clipping in. Secondly anticipate your stop, take your foot out early and rest it on the top.