I know this is just a snapshot, and you guys said that the minecarts will have new mechanics, but I'm pretty sure it ISN'T supposed to work like that.

When animals (e.g., pigs) ride a minecart NEAR lava, there is a bug where flames just start to appear. They don't get burned, sure, but it's stil a bug. Another bug is when you get burned when you're just CLOSE to lava in a minecart. Also, it's almost impossible not to get derailed, even with just ONE powered rail. And even if you can get derailed with just ONE powered rail, you can't even get UP a small hill with one. That seems ironic. I do love the realistic "jump" feature for the minecarts and derailing feature are realistic, too (but people will hate it), except it should be sensitive to weight, not speed. Probably next you should make it immune to lava... Anyway;

People I've asked said it's not a bug, but in my point of view, that is an extreme bug that needs to be fixed. The minecarts are wild and the mechanics are bugged.