I've been given an unofficial medium stub/cursive-italic (in Binder-speak) from ChartPak, and really like how the line variations add "character" to my handwriting. So now I have two more factory nibs coming (a Waterman Charleston stub and a Parker Sonnet medium italic), and am planning to get a stub or cursive-italic nib from Richard Binder.

Besides aesthetics, cost, and return policies, are there any differences between the stainless steel and gold Pelikan nibs? Can a layperson tell? How about an experienced calligrapher / nibmeister?

It's a question of personal preference. A steel Binder nib will be fantastic and a gold Binder nib will be fantastic. I like the feeling of gold and treated myself to one of Richard's .6mm Pelikan stubs this Christmas--it's absolutely wonderful.

I have a Pel steel-nibbed 200 and I swapped the nib out with my gold-nibbed Athens--it's a bit more to my taste, but frankly they're both great.

If money's not a giant issue, get one of each nib! You can swap back and forth to see which you personally prefer. If money's a factor, you might as well start with the steel unless you already know that you like gold nibs better. I find the difference fairly subtle in Pelikans. And you can always get a gold nib later and swap it out.

What do you mean by "feeling of gold" as compared to that of stainless steel?

Why not buy both, try both, and sell the one you love less (I'm sure you'll love them both)? As they're easily swapped in & out, I have a hard time believing that one of the many Peli-fans here wouldn't snatch an almost new Binder nib.