prev() is supposed to return the unique preceding siblings of the selected set, but it doesn't work correctly. It seems to check the tag and/or class name instead of comparing the actual nodes.

E.g.:

<div>
    <span>1</span>
    <span>2</span>
    <span>3</span>
    <span>4</span>
    <span>5</span>
</div>

If you now do:

$('div span').hover(function()
{
    $(this).prev();
});

The returned set only contains the span node immediately preceding the hovered element, not every span node preceding it.

This happens in 1.0.1, by the way, though that's not an option in this form.