NVIDIA Shield owners are being greeted by a quite sizable update in terms of download size, but not necessarily in the number of actual changes. Tonight's 460MB update is bringing a fix for a bug that prevented moving apps to the SDcard through the device settings, and a fix for using the bumpers as volume buttons (I highly recommend using this setting).
Further, it improves the audio latency and security when using GameStream to play games over the network. Improvements all around, and one you'll want to grab next time you open your Shield. Head to the settings and hit "check now" on system updates if you haven't been prompted.