Water deteriorates everything, brakes wear out quickly and dirt gets into the shoes and ruins rims, bearings get water in them and the shifting system will get dirty and require more maintenance. I ride all year and in all types of weather, I keep my long distance bikes and racing bikes as clean as possible, if I get caught in the rain, I clean and maintenance them before any problems arrise. I commute to work most of the time and have a commuting bike which is built up on a 26" mountain bike platform, I used all LX and XT mountain components because they are more tollerant to dirt and water. Commuting really is hard on a bike, why would you want to put your prize ride through that, I ride my good bikes to work in good weather, but I try not to use them as a work horse.