I'm one of the ones who went over to iPernity and set up shop there, alhtough without abandoning Flickr. At present, I'm using both. The new Flickr design remains incredibly clumsy to use on an iPad, which is where I do most of my photo-viewing. My iPad often crashes when attempting to load other photographers' photostreams or favorites. And I still dislike not being able to control how photos are displayed on my Flickr page; the ability to do that is one of the things that I find attractive about iPernity (and the old Flickr).
That said, the Flickr redsign for the iPhone is excellent and easy to use. And the tile-view works OK if you're viewing photos on a PC with lots of memory and a fast internet connection. Also, there's still a lot of activity on Flickr these days, even though it's more cumbersome to comment on photos and view comments posted by others. In that regard, iPernity is somewhat lacking. My photos don't get the views or comments at iPernity that they do on Flickr, which suggests to me that there has not been the mass defection and that people are finding a way to make the new Flickr design work for them even if it does not work as well for commenting purposes as the old design.
We'll see how things turn out... I do wish Flickr would address preformance problems for the iPad.