Don't ask what you can do for LuaTeX, but what LuaTeX can do for you.

The following video is a little old (2007), but it gives a flavor of some of the neat things that can be done with just a single LuaTeX feature, "attributes":

http://river-valley.tv/luatex-attributes/

(executive summary: attributes give you the power to transform portions of the document, from characters to specific words or paragraphs or the whole document in various ways, like assigning them a certain color)

And here is something that covers LuaTeX from a more general perspective:

http://river-valley.tv/luatex-a-users-perspective/

(executive summary: programming TeX directly is hard, doing the same in Lua is easy, and LuaTeX lets you program TeX in Lua)

Hi thingie, thank you for your comment; you are right that the slides were just to aid a lot of talking. The presentation was held at last year's EuroTeX (2009) conference and was quite technical with a lot of discussion and the talk was prepared within a few minutes before the talk. I just wanted to present the way I use LuaTeX and the problems I encountered while hacking. I try to sum up all this (with solutions) on my german blog www.luatex.de. I am sorry that I can't give you a better answer then "you should consider attending a TeX conference".