I write a lot of papers these days (articles, thesis, …). Often I need to fix issues/errors/typos from dead-tree-printed-version annotations to my LaTeX sources.

Unfortunately, isearch-forward (C-s) is not really convenient for this purpose since I use fill-paragraph (M-q) all the time, so that the consecutive words I'm looking for may as well lay on different lines.

Here is a quick solution : set search-whitespace-regexp to ”[ \t\r\n]+” (via M-x customize-option RET search-whitespace-regexp RET). It won't help for C-s, but isearch-forward-regexp (C-M-s) may do the trick as well. The only drawback left is when you search something that contains regexp meta characters, but I can live with it for now.

An obvious solution would be to write a command that performs isearch-forward-regexp but with a slightly modifed isearch-mode-map that would insert escaped meta characters automagically.