I like trains! Another good addition for the minecart update would be wooden and stone detector rails. Stone only sends a signal when a player is in the cart while wood detects only empty carts. Carts also need a speed increase. Perhaps 16 blocks/sec instead of the current 8.
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http://www.minecraftforum.net/topic/1117337-smarter-minecarts-non-abandoned-mineshafts/