Any significant program uses collections heavily, so most languages have several collection types - usually at least one sequence type and one dictionary type. Many languages have more, but library effort is limited, so every language omits some useful collections. As long as there are good alternatives, it's not a big problem.
Ruby doesn't have lists. RLisp borrows Ruby's data structures, so it doesn't have lists either. But it's a Lisp dialect! How can you have a Lisp without lists?
Pretty easily, it turns out. Despite their historical importance, lists don't have much to do with Lisp being Lisp. Their most important use is to represent S-expressions - but they aren't the only data structure that can do that. The important feature of S-expressions isn't that they read as lists - it's that they read as something simple and flexible and easy to work with. Vectors have all of these advantages, so RLisp programs are made of vectors instead of lists.
This is not traditional, but it's not a bad idea. Sure,
cdr are more expensive, and those are common operations on code, but performance of code manipulation is rarely a problem. And vectors are smaller than lists, which recovers some speed, and makes it cheaper to keep code around for debuggability. So I think other new Lisps should consider using vectors instead of lists.
I don't mean to suggest that lists aren't important. They are the functional sequence data structure, and every language that intends to support functional programming should have them. But RLisp is in its infancy, and it's forgivable if it doesn't have lists yet.
On the other hand, there's no excuse for its convention of writing close parentheses on their own lines. They look so lonely! More to the point, they waste space, separating the lines that have actual code. This is just as annoying in Lisp as it is in C, and there's no reason to do it in Lisp. Let indentation show program structure, and leave the parentheses at the ends of lines, regardless of whether they delimit vectors or lists.