Visual Studio 2013 Update 4 CTP 1 (man, that's a mouthful) is ready to download, and comes with numerous fixes, and features. CTP stands for Community Technology Preview. So, think of it as a beta. There will be bugs and issues - stay away if you're looking for stability.
The charts now have three different types: Stacked Area, Area and Line. These let you track trends across one, two, or four week intervals. The charts can be used to make a dashboard that provides a lot of useful glance-able data.
Pull requests, very popular in Git, now come to Visual Studio Online. Devs can use Pull requests to merge and review their code through feedback from other devs. Devs participating can leave comments, and can approve changes with a thumbs up. You can read more here.
You can now see the backlog and boards full screen. There is also a context menu that lets you move items on your backlog. Additionally in the web access mode, you can search for an area path.
There are C++ performance improvements, and a way to find GPU bottlenecks in C++ applications. C++ improvements are always welcome, as Microsoft has a tendency to treat C# better and let C++ devs wait for features.
You can read more about CTP 1 here, and download via the link below.