Using it for several months and liking it a lot. No shims, just PATH entries. And the slight overhead introduced by shims is gone as a result.
And because it's written in Rust, not going to lie.
It's even said almost at the top of the README.md in the "30 seconds demo" section:
"The following shows using mise to install different versions of node. Note that calling which node gives us a real path to node, not a shim."
https://github.com/jdx/mise?tab=readme-ov-file#30-second-dem...
So yes, mise does not use shims. It only manipulates $PATH. I did benchmarks a while ago and that definitely and consistently has shaved some milliseconds off of the startup times of my tools.