Carousel is backed by a huge storage array, and automatically backs up every picture. The author seems to have missed the critical elements of how it works!
The only selling point so far is that if someone else uses it to send you pictures, it's slightly easier to save them. Otherwise it's really limited - you can't even do Flickr 1.0 things like group items from multiple days together.
I'm assuming there's a plan to make it more interesting but so far I've had very little reason not to just open the familiar Dropbox app.
If yahoo shuts down Flickr tomorrow, it's users are screwed. If Dropbox shuts down tomorrow, all my pictures are on a handful of drives. Again, major difference in how it works.
Dropbox turned down buying Everpix last year, who had been an extremely promising photo management startup---because DB we're working on this. Most relevantly, the author of this article gives lip service in the first few paragraphs to the idea that design is how the system works, then reviews them based on the surface UI. He doesn't seem to look at the sync protocols of sync-focused apps!