I suspect that in no small part the performance edge is due to Mike Pall's LuaJIT, which absolutely thumps other dynamic language implementations.

And even the reference Lua interpreter is very fast -- it's small enough to fit entirely into a CPU cache.

This is besides the point. Judging platforms using trivial benchmarks is utterly useless.

Also, I think they shouldn't have made it the third sentence anyone reads about their project.

Yes and i was seeing the first comment to emerge here that went "uh yeah, lua is sooo fast and lean, the software will be soo fast as well" which may just be not true at all :P

The speed claim should probably be replaced with memory numbers. We are using luvit on a project because it uses much less memory than node.js and yet allows the team to use a familiar programming model.

Right now our project weighs in at about 4.5 MB RSS with statically linked in openssl. :)

If you're just using OpenSSL for primitives, look at PolarSSL. I, a total newb, managed to wrap the SHA functions without too much fuss before I moved on (long story).

https://github.com/jchester/lua-polarssl

Comparatively how much memory was Node.js using?

28MB - 35MB depending on the GC cycle IIRC.