As described by Microsoft's Windows Insider head Gabriel Aul, one of them offers some updated color options for Windows 10
"We got a lot of feedback on the default color for Start, Acton Center, Taskbar, and Title bars and that you wanted to be able to change to reflect your preferences. This feature is now available (though still early) in build 10525 for you to try. This is off by default, but you can turn it on by toggling this (Settings > Personalization > Colors)
In addition, Aul says there's a new memory management feature to try out:
"In Windows 10, we have added a new concept in the Memory Manager called a compression store, which is an in-memory collection of compressed pages. This means that when Memory Manager feels memory pressure, it will compress unused pages instead of writing them to disk. This reduces the amount of memory used per process, allowing Windows 10 to maintain more applications in physical memory at a time. This also helps provide better responsiveness across Windows 10. The compression store lives in the System process's working set. Since the system process holds the store in memory, its working set grows larger exactly when memory is being made available for other processes. This is visible in Task Manager and the reason the System process appears to be consuming more memory than previous releases."