Giles Turnbull is onto something with his latest comment on the Finder UI shown at WWDC 2007:
Do you like side-scrolling? Hmm. Me neither. I don’t expect we’re going to make much use of CoverFlow in the new Leopard Finder, then.
Horizontal scrolling usually gets a thumb down from usability experts. To be fair these experts typically focus on reading text online and there is some precedent for CoverFlow’s UI emulating the experience found when one browses art in a museum. Giles picks this approach apart rather nicely though:
Steve Jobs made everything look so neat in his WWDC demo, but his dummy folders full of dummy data are just that - dummy content, designed for demo. His folders were crammed with colorful, varied documents that conveniently showed off every new feature Steve wanted us to see. But, a lot of people have much messier folders, with an order of magnitude more files inside them. You think you’re going to browse through hundreds of files, one-by-one, in a graphical side-scrolling list view? No way. You’re going to search, right?
Which is a scary proposition at the moment given that Mac OS X’s search solution, Spotlight, has been going through a rather negatively backlash in the Mac community that started after the initial love affair with Mac OS X 10.4 wore off.
Self-guided research on horizontal scrolling issues:
- usability.gov - (Google’s HTML version of a PDF on Scrolling and Paging)
- Acessibility 101 in the UK claims users hate it
- Adobe’s Developer Center frowns upon it
- One of many times Jakob Nielsen has recommend against using it
- An older page from Jeanne DeVoto that at least tackles the issue with some substance in regards to reading and line-lengths
As you can see there is a lot of talk of avoiding horizontal scrolling but few of these pages cite the numbers or research they’ve based their recommendation on. Your best bet for a starting point might be doing a Google Scholar search.