I tried slimv recently and couldn't get it to work with Racket. There's a swank Racket project on github but it was extremely buggy. I also tried mit-scheme and it was buggy as well. It randomly freezes and I don't know why. (latest vim, etc.)
What do you use it for? It seems if you're using common lisp it's perfect, for everything else it works "in principle" but not really.