I have shimano acera index shifters and no problems at all. The bike is stored in warm place, but ridden all year - rain, snow, hot hot heat - no problems. All I do is adjust shifters in the spring and in the late autumn (when it gets cold). However, our winters are usually warmer than -10 degrees C (not F), with little snow (and lots of wind and wet weather).
And yes, like MileHighMark said: good quality cables and cable guides. If they have to be more slippery, use thin oil, not grease.