I spent a little time trying to figure out why this option was not working for me.
At first I thought it was because I'm using HTML code to customize the thumbnail text, but it seems that works just fine.
The issue turns out to be that you can enable this option in a "Categories" type view, but if you change it to a "File List" view the option disappears (which I had not noticed) but the alphabet across the top of the view is still displayed - it just doesn't do anything.
Would it be possible to have this option added for "File List" views?
I find it quite useful when a view has a lot of content to display.
