If you were a heavy bundles user, you are a bit nailed. They deleted all bundles and started “stacks.”
Here’s a video about stacks.
Stacks makes sharing bookmarks with your class more visual.
Otherwise, your links are all still intact.
There are other enhancements to the look and feel. Creating an account is easier.
It’s nice the site was picked up with folks with deep pockets and a vision of what to do with social bookmarking.