The problem is that people become complacent about clipless before unclipping becomes second nature. For the first week or so, you're paranoid about falling over so you unclip early and never have a problem. But then you get complacent, suddenly need to do a panic stop, don't think about unclipping, panic more as the bike starts to lean, and eventually fall over. Seems like the 2nd or 3rd week with clipless is often the trouble spot.

One way to minimize low-speed falls is to trade the stock SH-51 cleats for the SH-56 multi-release cleat, and reduce the release tension on the pedal a bit. Not to the point where you're pulling the shoes off the pedals with every rotation, but just to the point where a paniced yank will allow the cleat to release.