Well, the docs do start with a walkthrough of a simple application: http://www.luminusweb.net/docs

You can really judge for yourself how it compares to the alternatives you're familiar with.

In terms of memory/CPU there are plenty benchmarks out there such as the benchmarks game site http://benchmarksgame.alioth.debian.org/

A small Luminus app will take around 100megs https://groups.google.com/forum/#!topic/clojure/mQbcz82I7iI so that's pretty lightweight by most standards.

In general though while people seem to be obsessed with benchmarks of all kinds, performance is simply not going to be an issue for the vast majority of sites out there. The real question is how productive your stack is and how easy it is to work with.