Compile time. For my 9k lines project it takes 20 sec to compile in debug mode and 1 minute in release. Wich is insane because I have to do a lot of runs to test things(where cargo check can't help).
I tried to change some constants in random places(in 1 line each time) and on average it's ~10 seconds
Also compilation unit in rust is a crate. I guess if your app can be separated in different crates it can ease the pain.