I've never used Speedplay so can't comment about them. I have used SPD with walkable MTB shoes and dual sided pedals and have nothing but good to say about them. Multi-release cleats and adjusting the retention setting to the lightest point that prevents accidental clip-outs and they require so little effort to disengage that even if you forget you are clipped in, you will feel only a light click as long as you don't try to step off straight forward or straight back. You are not "locked to the bike" as the fear mongers like to claim. I had a MTB mishap last weekend where my bike and I parted company and I became unclipped well before I hit the ground, with no conscious effort on my part, even though I had felt secure hopping over rocks and roots for the previous hour.

If you fall from a failed unclip or otherwise, DO NOT put your hands out. Your best bet is to keep your hands on the bar and to tuck your chin toward your chest on the side away from the fall. Your hip, ribs and shoulder will take the impact which will spread the force out over a much greater area than the bones of your wrist and forearm. You can practice this in a number of ways. One of the best is to find a grassy area with a moderate slope. Stand sideways to the slope so you will be falling uphill. Bend your knees slightly and hold your hands out in front of you as if you were about to pass a basketball. Focus on keeping your hands still while you turn your head slightly away and tuck your chin then allow yourself to fall sideways. Exhale as you land. You'll be surprised how little it hurts. If you can get a bit of a roll from your hip to your shoulder, the impact will be even less. If you have access to a gym with a floor mat, that is also a great place to practice.

Another good skill to have is the track stand, the ability to come to a full stop with both feet on the pedals while balancing the bike. You don't have to be a pro who can hold a track stand like a statue for several minutes, just being able to maintain a slightly wobbly balance for a few seconds will do. I've had a few close calls with cars pulling out, pedestrians stepping in front of me, or right hooks where I have stopped for a couple of seconds then proceeded around them without ever putting a foot down.

Remember that clipless systems are mechanical devices and require cleaning, lubrication and maintenance. Clean them well and inspect them for wear. Excessive wear or damage is a reason for replacement of the cleats or both cleats and pedals. If all looks good, make sure that all screws are secure and that the tension adjustment (if there is one) is set equally and to your liking. Lubricate lightly (I use the same dry wax based lube I use on my chain) and do a few test clips just to assure everything is operating smoothly.