(it's worth noting that MS initially said they wouldn't release 15002 due to "break" bugs, but were essentially forced to do so by insider pressure as there hadn't been a build for over 2 weeks due to Christmas.
Another majorly important new feature (initially released in 15002) is a new method of display scaling for applications *cough Adobe Photoshop *cough* which haven't previously dealt well with high resolution displays under Windows.
Amongst the raft of other new features, fixes and changes (available to read here) MS have also changed how Windows deals with memory managemet in the desktop version of HyperV, meaning more available memory will be used, or rather made available to virtual machines than in previous versions. This makes it far more feasible to run more than one or two virtual machines on a "normal" Windows 10 desktop without everything running out of memory. (Windows achieves this by reducing the amount of memory it marks as reserved for the host OS and applications)