Two years ago I was casually learning Rust by night while by day I was extending a scheduler I had previously written in C. I kept wishing I could switch, because I kept having to handcraft in C things I would have gotten for nearly free in Rust.
Now, we're designing the Rust replacement for that C program, and it is taking all my will power not to start coding it: that job falls to someone else, and I am wistful about it. Not because I am going to miss the C code, but because it would just be so much fun to do in Rust.