Yes. Ridiculously. (I don't know the actual numbers. I just read this enough around here to be pretty confident in my answer.)

The chip that stores the swap partition is really fast (EDIT: Read post below this one. I need some schooling in my N900 partition knowledge). The chip that stores the rest of the stuff is a bit slower, but still pretty damn fast. The eMMC chip (the one where MyDocs sits) is slower still, but still, as I understand it, faster than the SD cards.