A quick disclaimer: I'm really a Lisp / Scheme noob, but I'm learning them both for academic purposes.
That being said, at first the parens bugged me a little bit, but as I got to developing more applications, the more I really grew to LOVE the parens. To me, they introduce a certain purity to the programs that I write; it's like every s-expr is a single thought and every function is a train of thinking. Beyond that, an additional benefit that I've found is that I can hold MUCH more of a program in my head when they're organized this way. I think it has to do with the chunking theory of memory - I don't have to remember the particulars of each chunk; just what each chunk did.
Anyways, it's a big enough attraction to me now that I regret not having them available in my day-to-day languages.
As peculiar and different as lisp is, the difficulty of learning it is highly overrated.