I don't really like this concept, but I do like this guy and his other work.
What I don't like:
It isn't obvious that there are other thumbnails other than the first one. If a user wasn't aware that there are other thumbnails to view they would never think to hover over the image.
Your critique seems to be focused on the wrong details. The author was not demoing their ability to indicate there is a mouseover action. They were indicating their ability to create a compact, intuitive (once hovered) technique for browsing thumbnails. Your issue can be fixed in a number of obvious ways, but the behavior once activated is a non-obvious contribution.
You're right – the intent is to demo the interaction when hovered and I did not spend any time designing the resting states. If this were to be used for something like a gallery thumbnail I think it's perfectly fine to not promote the hover preview at all. Users would discover it naturally as they mouse over to click on the thumbnail.
However if it's important the user discovers what's in the stack, this could be communicated visually like http://cl.ly/image/1c041l2e1S0O
I think an obvious stack (perhaps even more obvious than depicted in your screenshot) would help. Another thing you could consider is having the stack give a little more affordance as the mouse pointer approaches. Perhaps it could expand a little to indicate "hey, there's a behavior over here!"
Sure. One would be when you mouse-enter, a small circle or bar appears that fills in as you hold your mouse there, indicating something will happen once it becomes full. Another would be to have the other thumbnails "peek" out on mouse over, which provides the user a place to click to activate the browser mode to see them.
I love your second idea; nice one. :) (Not sure how to make it work for mobile, though, unless you have it "peek" out all the time.)
The first reminds me too much of dcurtis' "Kudos" circle, though, where something happens because you left your mouse in the wrong spot for too long; it's nigh-infuriating sometimes.
I like the concept. However, to me, it was a little bit too easy to accidentally move my mouse outside the thumbnail area when trying to look through some pictures.
Could you try extending the mouseover area beyond the images themselves? I'm not sure if that would be more intuitive, but I think it's worth trying.
This is basically unusable with a mouse pointer because the bounding box is too small. The user interface is also non-obvious, at first I didn't know that I could move my mouse around and I would not have discovered it if this wasn't a tech demo.
Agree...an improvement would be to add a transparent arrow on each side and only advance/go back when the user clicked or held down on the arrow. That probably exists already...
Interesting idea, the interaction would get very difficult with more pictures in the stack. Also lacks a way to work in mobile. But you are really onto something here, would be interesting to see how this can be improved!
I like the concept, but the thumbnail should somehow show that there is a 'stack' of photos that you can page through. At first glance, it's not obvious that you can hover over a thumbnail to see more.
I like this, but could you make it a bit slower? Slowing it down would make it a little bit more accessible for those who have mouse trouble. Also keyboard keys!
Apple's had a less fancier implementation for quite a while now — thumbnail scrubbing in iPhoto and FCP on the desktop. I don't have any iOS devices to see if they have touch versions of their scrubber but I do remember seeing one on an iPad demo video some time back.
What I don't like: It isn't obvious that there are other thumbnails other than the first one. If a user wasn't aware that there are other thumbnails to view they would never think to hover over the image.