As I get more into using Vim and learning all of the keyboard-based commands, I occasionally run across something that doesn't act quite the way I think it should. Case in point: when using the FANTASTIC NERD Tree plugin for Vim (it's a project browser much like Textmate's Project Drawer), I found a (small) bottleneck in my workflow. I like using the H, M, and L commands to quickly navigate to the top ("High"), middle, and bottom ("Low") parts of the screen (gg and G to move to the top and bottom of the buffer are also great).

But NERD Tree overrides H for toggling hidden files on and off (in the NERD Tree browser only; regular files are untouched). I couldn't have this, since my file browser often has lots of folders open (I know it's not ideal, just a hard habit to break). So I plunged into the NERD Tree plugin's source (~/.vim/plugin/NERD_tree.vim) and found the line I needed (around the 120's in my version):

call s:initVariable("g:NERDTreeMapToggleHidden", "H")
needed to change to:
call s:initVariable("g:NERDTreeMapToggleHidden", "I")

I chose I since the NERD Tree browser in not modifiable anyway (the usual use for I is to enter Insert Mode at the start of the line), but that's obviously not necessary. Now I'm navigating to my heart's content (well, to the top of the screen, at any rate).