Great feature!
In case you're not aware, this feature could be worth tons for other replacements, that is, apart from delimiters.
If I was to do this, I'd add an option along the lines of "whole words only", referring to at least one space around the specified criterion. This way you could, in the case of your example, you could avoid changing "this/that" to "thisthat" when replacing "/" between words.
Also, case-sensivity could be an option.
In the end (out of boredom, I suppose :-) ), you could go ahead and check the find and replace dialogs in Office programs such as Word, Excel, Access - these provide different levels of sophistication regarding the subject of F&R. :
