Anything new I should know about? I think last I remember I was out of energy and couldn't do anything? (May be misremembering). Is it worth jumping back in?
Returning Player from 2014

From the sound of it you were from the mist era, so here are the good news: no more elevator cost, you can play for as long as you want.
HOWEVER
Heating weapons, especially 5* weapons that require the radiant heat crystals, which are extremely rare, you don't have any 5* weapons already fully heated I would suggest you play another game, SK is not worth the grind in its current condition.

@Midnight-Dj
The grind shifted from "playing the game" to "getting the most powerful items". Back in the mist days, you could only play 10 free levels a day, then it normally cost more resources than you would gain to play more (unless you played a handful of levels that provided enough profit).
Lots of players ignore the fact that buying radiants from the supply depot is less of a grind than just being able to play the game previously, especially considering the introduced "elite" mode at the same time that mist was removed provided higher crown payouts. Also, fully heated 4* items aren't that much weaker than 5*. The only strategy that returning players should be aware of is: Don't upgrade weapons unless you have the resources to fully heat it (5* weapons are ~450 radiants to get from lvl 1-10). It's generally a decrease in damage output until lvl 8+.
Here is a curated history of all major changes to the game:
https://wiki.spiralknights.com/History
As you can see, there haven't been many updates recently. But there have been a few decent updates since 2014: gunner update, new missions, sleep levels, etc.
The game is (approximately) as fun as ever. Sure, jump back in. Welcome.