[kixiQu]

> selecting multiple occurrences of a word, and then editing in place

I'm sure there is a way to do this More Properly, but the kind of thing I'd do is:

:%s/user/account/g

:%s/User/Account/g

If you wanted to check each one interactively, end with gc instead of g.

Vim is the reason I'm real confident with regexes, even nonsense with grouping and quantifiers etc. etc., and while I can see people not wanting to have to acquire that power, I must say it's also very handy outside of text editing.

> selecting all the above occurrences, and pasting them somewhere for an interface declaration.

I don't really understand the behavior desired here, but I'll bet there's something similar.