I am far from an expert at Lua, but I have done a couple of semi-serious projects in the language and will try to recall specifically what I didn't like:
- Simple-minded people seems love Lua due to Baby Duck Syndrome and too much World of Warcraft farming, instead of education.
- Yet another boring, badly designed, slow scripting language. Nothing to see here.
- No, wait! Lua managed to screw royally even where other scripting crap works nice - there is no list/vector type in Lua: you can't access elements sequentially or by an integer index. That needs some talent!