Any "must read" docs for Linux-head buying an Android device?
Android != GNU/Linux. That is a common misunderstanding.

You will never have the same Linux experience like you had with your N900 running debian. Sure, you can install busybox, sshd, maybe rsync and fuse should also be possible. Latex for example, with it's various dependencies will be hard to get running. Mostly because there is no package manager for Android and the toolchain (i.e. libc) is not the same. It's all technically possible, no major blockers. There are even ways to get debian/ubuntu running on Android, even side-by-side. But this doesn't seem a practical solution, more a proof-of-concept for now.