This morning's system update went well :-)
There aren't any major visible new features in the new system -- it was primarily an infrastructural change. The operating system on our underlying servers has been upgraded from Ubuntu 14.04 to 16.04 (so we had to rewrite all of our upstart system jobs as systemd ones, which was... fun). The sandboxes where your code runs have been kept as Ubuntu 14.04, so that your code doesn't break due to the system it runs on changing unexpectedly.
A future update, hopefully soon, will enable a 16.04-based system image that you'll be able to opt in to use when it's convenient to you. There's also a big new feature that we're working on that required the OS upgrade -- more about that another time...
There were a few minor changes beyond that: