The February 3 blog post outlining what's new mentions fixes around periodic app crashes and other memory-related app errors. The Git client for Windows should work with this build. The F12 Developer Tools should now load correctly in Edge. And some DPI tweaks should fix the jumbling of desktop icons as of this build.
The post lists, as usual, known issues with this build. Testers should be aware that resetting a PC with this build (and the previous 14251 build) will leave the PC "in an usuable state," and there's no workaround, though this should be fixed in the next build, Microsoft says. The front-facing cameras with PCs using Intel RealSense also doesn't work in this build.