Two common task performed when editing with Emacs are (a) Visit some file and (b) search for some text.
In my case it often happens that the path of the file to visit or the text to search for is previously copied to the kill ring (or system clipboard), so that I, intuitively, yank it with C-y.
This works OK when the operation at hand is to visit a file, but it doesn't in the search case, because in Isearch mode, C-y is bounded to another command: One that takes the text from point to the end of line as search text (which is of little use, IMO).
Personally, I find this behavior inconsistent/annoying: I would expect that C-y within Isearch add text X to the search text, where X is the text that would be yanked in normal editing.
One solution to fix this would be to swap the bindings of C-y and M-y withing Isearch mode. Of course I can do that in my .emacs, but if you agree with my reasoning, it could be make the default.