I'm interested to hear dissenting opinions, but you'll need to back them up with specifics.
First some preamble. One of the fundamental design features of Scheme is lexical scoping, at the time a relatively unusual feature. Lexical scoping greatly simplifies program comprehension and compilation. In a lexically scoped language, a binding -- that is, an association between a name and a value -- is only visible in the scope in which it is defined, and any scopes within that scope. This means the textual source of the language determines which bindings are visible -- simple and no surprises.
The save function in R doesn't save a value, it saves a binding. When you call load you actually add a binding into your scope (local or global scope? I'm not sure and the docs don't say.) This is absolute madness. It means you need to know the name that was bound to the value when it was saved, coupling the code that uses the saved value to the code that produces it. Imagine programmer A writes the code that calls save and programmer B loads values. They agree on a name, but then programmer A changes that name ... and breaks programmer B's code!
Now you might argue this is a standard library issue, not a language issue, but I argue the two are so tightly coupled you can't consider one in isolation.
Language and standard library are tightly coupled, but problems with the standard library are _much_ easier to fix than problems with the language.
As the above suggests I don't hold R the language in much esteem. What it had was familiarity for people who had used S, and now, years and years of accumulated libraries. I don't believe there were any technical features in R that led to success. It was purely social: a free and open source language that was close enough to an already familiar tool.