It's probably worth mentioning that all the delete functions he points out(all of them for that matter, ctrl-k, etc) are actually cut's, so you can paste them back as well.
I find Ctrl-u especially useful when I'm halfway through with a command, then I realize I wanted to do something else before executing said command, so I cut it- then paste it back when I need it.
* Ctrl + y to paste anything back
$ aaa ^U
# now "aaa" is the only thing in the kill ring
$ bbb ^U
# now kill ring is ["aaa", "bbb"]
$ ccc ^U
# now kill ring is ["aaa", "bbb", "ccc"]
$ ^Y
$ ccc
# alt+y cycles through the kill ring
$ bbb Alt+Y
$ aaa Alt+Y
$ ccc Alt+Y
$ bbb
etc. This likely feels completely natural if you're an emacs user. I don't know what the equivalent vi thing is.
