Not to start a Lisp-vs-Lisp side-conversation here, but if we're going to go with a 'modern' Lisp, I'd prefer one that doesn't add syntax and which supports proper tail-call elimination.

It's not like we have a lack of those, either - Racket's my personal favorite; aside from the robust standard library, the scoped languages give me hope that the 'Lisp curse' has finally been reversed.