LuaJIT bucks the trend of slow-warmup JITs. It is extremely quick to compile and load, and its interpreter is very fast -- faster than the JIT-compiled code from LuaJIT v1 IIRC, and certainly faster than the interpreter of Lua.
It wasn't until LuaJIT that I realized that JIT didn't inherently have to be these slow lumbering beasts that take hundreds of milliseconds just to wake from their slumber.
Yet I've witnessed Lua 5.1 launching faster than luajit for some of my use cases.
My point still stands though. Don't just use LuaJIT thinking it will magically make things faster in all cases. If you are embedding, LuaJIT is a no-brainer. If you are using a stand-alone interpreter, measure if you care about reality.
It wasn't until LuaJIT that I realized that JIT didn't inherently have to be these slow lumbering beasts that take hundreds of milliseconds just to wake from their slumber.