What I want from case sensitivity is NOT multiple variables with different cases.
Of course not, this is not something you're actively looking for unless you really love trouble. But why is it so undesirable not to enforce different capitalizations? A warning could certainly be handy if you really want to enforce a consistant capitalization throughout your files. On the other hand an error seems too much for me. As another reason, I like the fact that capitalization only matters in readability. Using the same capitalization convention in a given project is a plus regarding readability. Given that I can't force 3rd party libraries authors to use the same convention as me, case insenstivity is the only way to really have a single capitalization convention even when using other people's code.
In the end it's not like it matters that much but really if there is an annoyance somwhere I see it in the case sensitivity.
I think a poll on users personal preference would be interesting.