Vim 9.0 Released With New Vim9 Script For 10~100x Execution Speed
Vim 9.0 has a lot of small additions while the big change is Vim9 for the Vim script language. Vim9 is focused on better performance so much so that "An increase in execution speed of 10 to 100 times can be expected." Vim9 script is much faster thanks to compiling commands into instructions for efficient execution. However, there is backwards compatibility breakage in some areas as a result of the Vim9 script changes and trying to make it more efficient.
More details on the changes to find with Vim 9.0 via Vim.org.