Thanks for checking!
To reproduce it just play with the scrollbars, as they all read out '0' when in their initial location.
You can use this change I made to the jsFiddle code:
One more difference in behavior between browsers I now spotted, is that the initial value of '0' is also something specific to Firefox (I have Firefox 4). Other browsers will read out the scroll distance from the left, no matter the direction.
For that matter, perhaps it's worth leaving .scrollLeft() along, and creating a new jQuery function called .scrollDistanceHorizontal() or something along this line, that will represent the scroll distance from the initial scrollbar location, no matter the direction.
This way, given an example situation where I have an LTR site with a slider script that scrolls a div from right to left by increasing the scroll distance, I would not have to make any changes to the script if I localize the site to RTL languages.
This could be nice. Thanks again!