Many of the changes are post-Skeletron, near as I can tell.

So what do you think? Is there enough interesting stuff to make it worthwhile starting all over with copper equipment, or are you planning to just load up your old world and play from there?

I was pre-plantera when the update came (still am, slowly collecting life fruits), and I just continued the old world. Most of the new stuff is craftable / buyable. Only new stuff that spawns on world generation are few monster statues and geyser traps. Not worth restarting.

What exactly are the geyser traps? Can I make them or are they like the boulder traps, which after two years still kill me every ten minutes. :P

I started new world, but I was waiting specifically for this update. A lot of new things in it for me, because I wasn't there for patch 1.3.0 (I was distracted by other stuff). It seems like there is much more wood in the world now :)

No idea, I didn't encounter it myself, obviously. But they are meant to kill you, which I can do without :)

There is a good summary of the changes, most of the new items with links to proper wiki page. 1.3.0 definitely deserves a new expert world, and I had a blast doing it with new character too. 1.3.1 is pretty minor upgrade in comparison. Beware hardmode underground desert, survivability is measured in seconds until very late game.

A 'trick' I use is to put the wire cutters in one of the quick-use slots, and periodically choose that as my active item for a second or two. The wires for the traps then show up and you only then need to snip a single bit of wire to disable the trap (but of course, you want all of the wire so snip every bit of it). Note that the boulder can still kill you: if you mine underneath it, it can fall on you. Mine the boulder itself to destroy it.

If you try the adventure map "Tale of the Terrarian", you'll find geyser traps in the hell circus area. Also some beehives (not the giant ones that serve as minibiomes) in the jungle area.

Oh, as soon as I get the clippers I never get hit by traps, but it's not like you get those right away.

There is A LOT of exploring before then, and A LOT of pressure plates you can miss.

Cool thing is last time I got done in by a boulder I got a black triangular headstone with a gold crown on it.
Think I'm going to use it as a cap on my base, if I ever get a new one built.

If you drop a lot of money when you die, you get a fancy golden headstone. I think it's at least one gold piece dropped, which means that you need to be carrying at least two gold pieces.

Until you get the wire cutters, just put a pressure plate or a dart trap or active/inactive stone block into that quick slot. I generally can harvest one of those puppies in the first couple caves.

So there is a connection! :D

Way cool and it makes sense. When it happened I was just starting so I didn't have any banks for the money thus I had it on me.

WTF, the game just started me on a cloud! There was no water underneath it so there was literally no way to play. The only way to get off the cloud was jump and that meant SPLAT! XD

That seems like a fun world to explore once you have a character that can slowfall or drop long distance without dying.

Alternatively, chop down a tree, plant its acorn (hope you do get at least one acorn), start building down a stairway. Chop more trees if you run out of wood (hence: acorn).

Platforms are more resource efficient because you can get two platform tiles per wood block. Also you can mine back some of the platforms you need to put, because even a noob character without items can jump six blocks but when building in the open you have to put each block next to another block.