Minecarts don't turn on curves in tracks, and gets stuck on slopes unless pushed.

When the minecart hits a curve, it starts moving backwards at the same speed it was at, and when placed on steep slopes on an normal track, won't move unless either being forced to via a powered track, or pushed by a player or mob. Also it derails from time to time. This is identical to how Minecarts worked in the 1.8 snapshots.