Yes, of course, and I'd much rather use something like it; and when it will support matrices with more than 2 dimensions, I will (or at least, I will look into

Yes, of course, and I'd much rather use something like it; and when it will support matrices with more than 2 dimensions, I will (or at least, I will look into it). In cases where I need more robust storage I already use HDF5 or NetCDF but they're a PITA to work with. Of course in-memory operations can be implemented efficiently, R does that too. But Python needs to parse CSV into numbers just like everybody else, and even if it's done in C underneath, it'll still be 'slow' (for some values of that word).