Use Lisp for its strengths, and other technologies for theirs. Server side CL, client side jQuery, Postgres on the backend, and your choice of caches, proxies and middle-ware in between.

I have tried nearly every other combination of New Thing and Hyped Awesome, and came to this conclusion: don't do everything yourself, and don't use technologies others are not investing big $ in. Anyone can push something to github and launch a nice tryfoo.org site, that doesn't mean you should use it.

FWIW, I am migrating my entire web toolchain to the JVM and intend to start writing servlets in Lisp. Let Big Business be my R&D bitch. JVM is good enough, and it's posh.