I have programmed in Lua for 10 years and recently I becomming to work with Lua and classes in a "Java-style", usign "30log" module by Yonaba (great job!) .
I recognize that is not a "true oriented object approach", but it works very well in Lua. But the real gain is that many concepts of OO in Java are very useful to code maintenance, specially from Effective Java, Refactoring and Design Patterns books (all for Java). And the code is straightfoward convertable to Lua.
I have written examples of all Design Pattens in Lua OO, but I´m busy to put in Lua-Users Wiki. I´m thinking to send to mailing-list.