I personally use CTRL + F for more "ad hoc" style searching of an Excel file, whereas the VLOOKUP function is much more robust, and lends itself to some automated applications.  In the past I've used VLOOKUPs extensively in maintaining reports, making it possible to update only one area of the file when information changes, as opposed to every individual view.  While this is definitely not a best practice (and not really something I even do anymore, now that I have access to other tools), it's definitely handy when you're attempting to hack something together to meet a business need on the fly.