Definitely yes. Players with fast reaction time can respond to the moves of their opponents in a quick manner and are, hence, better hockey players.
Yes, a quick reaction time is important for all hockey players, especially the goalkeeper. The reason behind this is that the hockey puck can move well above 100 mph on the pitch. Resultantly, the players have to react very fast and the goalkeeper has a very short window of time to react to an oncoming ball and prevent it from hitting the net.