Every time a new Terraria update trailer comes out, I find myself watching and rewatching it to try to pick out things that are new. The most obvious one in this 1.3 trailer is the mine cart. Now that it's here, it surprises me that it has taken so long. I can't wait to see videos of people making nutso roller coasters that span worlds. You know people will do it.
There are some other interesting bits, though for some I'm not sure if they are new (I never delved far into 1.2). The mine cart ride shows off timed lava resistance, more detailed environmental backgrounds, and a teleporter at the conclusion. It also jumps the shark. Har har.
Terraria update 1.3 is expected on June 30. That's only about a month away!