what is your intention with getting the index? Is it to “cycle” through class assignments while going through the loop (cos I can’t imagine you somehow styling <li>s specifically by their number?), like how the Rails cycle helper works (ActionView::Helpers::TextHelper)? That would be my own use case for this - and I imagine that most folks’ reason for getting the index would be to do the same.
So I could imagine something like this:
<li {{ bindAttr class='cycle( grey, white )' }}>{{ name }}</li>
Or even as part of the {{linkTo}}:
{{#linkTo user user class='cycle( grey, white )'}}{{ user.name }}{{/linkTo}}
I think having something like this built into Ember would make sense.