There are many things you could dismiss as style issues, but here is one relating to performance. Rust does not (yet) have integer generics. If I use Eigen (the C++ library), I can declare a matrix of size 6x9 and have the allocation live (cheaply) on the stack. I do this kind of thing frequently (not always 6x9), and in Rust I would pay for heap allocated matrices. The cost in performance can be huge. Maybe this will get fixed in the near future.
