Have you used vim? . is much closer to running a keyboard macro than it is to C-x z - only you don't have to record anything ahead of time, nor necessarily even realise until afterwards that you might want to reuse what you've just done. There's no precise equivalent in emacs. It's described here: http://vim.wikia.com/wiki/Repeat_last_change

C-x z is lame by comparison. Like, suppose you just typed in M-d h e l l o, and you press C-x z. It repeats the last command: self-insert-command. So you get an additional o. Thanks, Emacs!

More comedy: after you move the cursor, perhaps planning to use C-x z to insert another o elsewhere in the document, C-x z now replays the last cursor movement command.

(None of this is illogical, it's simply that C-x z is not, probably, very useful for editing text.)

With vim, on the other hand, pressing . would replay the word deletion, followed by the insertion of "hello". And you can use other motion commands to move about the file before repeating it again, allowing you to perform this operation in multiple places.