Now the flaps don't melt! The tiles don't fall off!

It's a major overhaul of the design they've been working on for a long time. There was talk of v3 fixing the problems in early v2 test flights. The booster is v3 as well which presumably is why they had some problems. I believe this is also the first time they flew the v3 engines with the plumbing fully integrated in a single piece housing they 3D printed.

Quite a bit has changed. Here's the highlights: https://www.spacex.com/updates#starship-v3

Biggest things changed are the plumbing inside the booster (much beefier, now supports starting all engines at once), and a new version of the engines, raptor v3 (more robust, and saves about 1 ton of mass per engine).

Cool image comparing the three versions of the engine. In addition to making the engine itself a bit lighter, moving all that stuff to the inside of the engine let them eliminate a whole bunch of heavy shielding in the engine bay.

https://ibb.co/pr0gx688