You simply use the normal Find dialog in Notepad++. They added an extra button to Find/Replace in all open buffers. Therefore, it's a 2 step process. FIrst, do initial "Find in All Files". Once you have all of the files/buffers open you wat to change, use the "Find/Replace in Open Files" button to make it happen. The buffers will be modified, but not yet saved, as a last means to revert.
The other advantage the NP++ Find/Replace has over Sublime, is the find results pane. The find results of each file are collapsible, which I usually use a a note-to-self that I am done with a particular file if I am sorting through a large list. Also, I think the find results pane highlights each found item as you click on it. This also serves as a placeholder.
I think Sublime could really benefit by adding some similar goodness. I think a "Replace in Open Buffers" option along with "Collapsible Find Results per File" would be my vote for an initial implementation. I am pretty sure the first could be done in a plugin, but the second would be a tweak to the find results panel needed in the Sublime core.