What programs is it not backward-kill-word in?
Edit: That should be close tab, not close window, c-shift-w is window.
(I've never really understood why there are keyboard shortcuts for things like "quit program" and "print". How often, if ever, do you want to do those things? Do they really need to be one keystroke away!?)
How is it not useful to have a keyboard shortcut to change focus between windows? Windows in vim refer to what I believe are called "splits" in emacs. The vim c-w stuff is analogous to c-x stuff in emacs.
As for close tab shortcuts in firefox -- I use it all the time. Standard work flow for me includes c-t, google.com, <misspelled word>, c-w, <correct spelling from "did you mean">.
This might be quicker: c-k, <misspelled word>, alt-enter, c-w
alt-enter opens a new tab with the search.
It's very useful in situations like this to know that Ctrl-Shift-T reopens the last closed tab, and you can press it repeatedly to continue opening less-recently closed tabs.