I don't know if that's intended or not, and I haven't found anyone complaining about it on here or any note in the Wiki, but I find it rather annoying that there seems no way anymore to be able to stop a minecart on a track.
Before it was possible to destroy the minecart from the inside. With 1.6 that doesn't seem to be possible anymore.
In 'survival' you can hit the minecart, and it shakes but nothing happens.
In 'creative' you actually destroy the track and any block below the minecart, but the minecart stays intact.
The problem is, if you'd like to get out of the minecart midway, you can only shift-click to leave and the minecart continues it's way, which basically means it's 'gone' and needs to be recovered by running after it to the point where it stops - which I find a bit odd and less practical.