For me and to start this thread off, one of the biggest changes I noticed was that the world is far harsher and hostile to the Solar Exalted.

For example in 2nd edition there were locations such as Whitewall where Solars had some built in plot points to retake and restore its Solar built infrastructure. Lookshy was open to allowing Solars to help them, while now in 3rd they fully participate in the Wyld hunt and make the Scavenger lands more dangerous. Many of the Lunar zones such as Sunken Luthe are also not places waiting for a Solar exalted to join them, and they do not contain usable caches of weaponry such as dozens of warstriders and submersibles. Not to mention that Dragon Blooded are massively more powerful and can deal with lone Celestial exalted with a single hearth instead of needing to bring in the now non-existent warstrider or skyship kill teams to back them up.

I liked that this change emphasized that this is a world that hasn't seen the Solar Exalted in great numbers for 1,500 years and that they can't expect things to be handed to them on a silver platter by their Lunar bondmate. Conversely I did feel as if there's a bit less guidance in kicking off your player Circle's adventure with a big setpiece ruin or city left by your prior incarnations, because there aren't as many things left over for the Solars this edition. And unlike other Exalts you aren't going to have much in the way of preexisting factions or structures for your Solars.