For one thing, I've come around to the view that syntax is waaaay over-emphasized in our current languages. The way I like to put it is syntax is a MacGuffin, "an object, device, or event that is necessary to the plot and the motivation of the characters, but insignificant, unimportant, or irrelevant in itself." You have to have some syntax to write programs, but not nearly as much as we typically use. I haven't dug into Om yet, but Joy feels like the simplest useful language. (BrainF*ck is simpler but harder to use, Lisp and Forth are more complex.)
For another, the concatinative systems seem to be simpler to reason about than Lambda Calculus-based systems (most current PLs.) What I mean is, these languages fulfill Backus' vision of FP systems wherein you can derive programs by doing algebraic manipulation of programs. (You can do this in any language, of course, but Joy et. al. seem to make it especially easy.) I suspect this has something to do with Category Theory (see http://conal.net/papers/compiling-to-categories/ )
All this to say, if you haven't already, do have a look at Concatinative languages.