Rust is a much smaller language and stdlib than C++ (though still quite large). Rust makes an effort to make many things explicit that are implicit in C++, such as numeric type conversions. Rust's traits are conceptually simpler than classes, especially if you want multiple inheritance. Rust's templates/generics are much closer to the core language than C++'s template language.
And then there are all of the safety features of Rust; while there is a learning curve, it is much easier to learn the concepts of lifetimes and ownership when the compiler is helping to enforce proper usage.
Are you talking about grokking the language and its more excotic concepts or writing code on it?
I have almost 30 years of C++ experience and about 6 months of Rust.
My gut feeling is that the languages are equally difficult to understand but that the experience of writing code in them is very different.
I'm sure Rust will have its own set of surprises as I keep using it.
But I can't believe they will be nearly as bad as those that C++ comes with. ;)
And then there are all of the safety features of Rust; while there is a learning curve, it is much easier to learn the concepts of lifetimes and ownership when the compiler is helping to enforce proper usage.