> Vim's hjkl make sense as you start using the tool. tmux's Ctrl-B for a prefix doesn't make sense, so that leads to remapping.

Hmm, I'm still confused:

* How do Vim's hjkl start to make sense? They've always seemed arbitrary. 'l' should stand for 'left', but it takes me right!

* How is a different keyboard shortcut less confusing than ctrl-b. They all seem arbitrary. You remapped it to ctrl-a. Maybe you were used to GNU Screen?