Hi!
I like to wear sandals in the rain if it's a reasonably warm rain. When it gets colder I usually wear shoes,
Crazily enough during the last two long tours that I've been on, I left my lightweight overcovers at home. One of those crazy save a little weight type decisions. Big mistake since it likely saved a few ounces of weight and it took the shoes three days to fully dry out.
Sandals are the best. Some people bring sandals and goretex socks so that they can ride in the cold wearing sandals rather then bring an extra pair of shoes.
~Jamie N
www.bicycletouring101.com