I have never used anything but speedplay zero, the learning curve was more about being clipped in than speedplay specific. I do have the keepcovers and I highly recommend them, I carry something to cover the exposed part were I to have to walk around in gravel or mud etc (imagine a small homemade shower cap fro each cleat LOL), if you do go with the speedplays my advise is to get the keep on covers and put them on before you ever use them as they will protect the wear you get in the cleat. mine don't last more than a year without the covers just from stopping, not walking around. The coffee covers don't offer wear protection while riding, only while walking.
The exit force required (at least in my zeros) is adjustable. It is very important to maintain the cleats though, keep them clean and examine the screws and keep the pedals clean, nothing extraordinary though. I now have 105s on my other bike and I have yet to try them out LOL, I suffer the same fear of the change. I would really prefer just to buy another set of pedals but I am too cheap and the 105s were free.