- Revamped profile tab
- Search for users and tags in the Explore tab
- Improvements to commenting
- User search autocompletes based on people you follow
- Visual improvements
- Speed optimizations
- Optionally share likes to Facebook (enable in your Profile > Sharing Settings > Facebook)
This is a decent upgrade and there are a few things to note. Instagram's rapid growth has been, in part, due to its Popular tab. Even if you were new to the network you could easily see stunning photos. The Popular tab is now called Explore. And this is important for product people to note. Instagram needed an easier way to find photos you might be interested in (such as an event or other interest) and also find users. And many would be scared to "mess with" the Popular tab. However, taking the most popular tab (the Popular tab) and adding those features to it really shows what Instagram considers important. They want people to discover people and photos easier than ever.
Also, cross-network "likes" is an interesting concept that we're about to see a lot more of. It will even be in Mac OS X Mountain Lion next month.
There are some hidden gems in this release to including this one from Keegan Jones.