As a more comprehensive answer.. It depends. Progress-wise you can still only really get to Yagluth. There are now caves in the Mountains, abominations in the Swamps (DO NOT GOOGLE THAT - that's worth experiencing blind) and tar pits in the Pains biome complete with a new blob variant.

If you were a builder, then there is quite a lot of new building blocks to make your builds even cooler.

Then, peripherally, some new foods and a few other bits.

Fundimentally (at least IMHO) the gameplay has not significantly changed, but going on another fresh run would deffos be fun, so I guess, good luck on your decision.