This does look quite nice. I always felt that the operator precedence / association rules in other stack languages were by far the most difficult thing to get used to, not the nonstandard symbols. This appears more inviting in that regard.
I do have to question the choice of right-to-left (array language) evaluation order. I've personally always preferred left-to-right (stack language) evaluation. I feel like right-to-left requires you to think to the end of a line before you start typing anything at all, as the first thing you type is the last thing that's evaluated. Left-to-right would also allow re-evaluating and visualizing the stack as you write each operator.
I do have to question the choice of right-to-left (array language) evaluation order. I've personally always preferred left-to-right (stack language) evaluation. I feel like right-to-left requires you to think to the end of a line before you start typing anything at all, as the first thing you type is the last thing that's evaluated. Left-to-right would also allow re-evaluating and visualizing the stack as you write each operator.