If at all possible, I would like to see a checkbox somewhere on the Join Data dialog box in ArcMap, a box you could check to get a join that was case insensitive.
Let's say you have two text fields you want to join and one of the fields have say, Camel Case type text entered while the other does not, and that you just wanted to do a "quick'n'dirty" test of something, then it's a tad annoying the default is a case sensitive join.